Applies to: Communicator 4.x
Operating Systems: Windows 3.x, Windows 95, Windows 98, and Windows NT.

ADVANCED COMMUNICATOR PREFERENCES

user_pref Settings for the prefs.js Configuration File

IMPORTANT NOTE: This page contains information regarding direct modification of the core Communicator preferences file, prefs.js. This file is located in your ...\Netscape\Users\{username}\ directory. Before making changes to this file, Netscape must not be running, you should always make a backup copy of the file before beginning, and the file should be edited from a text editor such as Notepad. Editing of prefs.js is not a procedure officially supported by Netscape, so do so at your own risk.
 

How to Modify the prefs.js File (Please Read First)

Before editing, close Communicator and make a backup of prefs.js, then open the original in a text edit such as Notepad. To add a line, simply type or copy it to a line of its own in the prefs.js file in the same fashion as other options already in the file. Keep in mind that parameters in this file are case sensitive (meaning that it does matter whether you type an uppercase vs. a lowercase letter), and spelling and syntax errors may cause the contents of the file to be deleted when you restart Netscape. So be careful and back up everything first.

This page documents preferences that can be set in prefs.js, but cannot be set from within the Edit | Preferences menu in the Communicator graphical user interface. The basic structure of a prefs.js entry is as follows:

user_pref("browser.cache.directory", "C:\\Netscape\\Cache");

In the above entry, browser.cache.directory is the parameter, and C:\\Netscape\\Cache is the value. Note that parameters are always enclosed in quotes. Values are enclosed in quotes when alphanumeric (containing letters or letters and numbers), however numeric-only values and true/false values are not enclosed in quotes. For example:

user_pref("browser.cache.directory", "C:\\Netscape\\Cache"); (alphanumeric value)
user_pref("browser.link_expiration", 10); (numeric value)
user_pref("browser.wfe.ignore_def_check", true); (true/false value)

Also remember that JavaScript is case-sensitive (it matters whether something is in uppercase or lowercase), and as a result so is prefs.js. An error in the case of a letter is equal to a spelling mistake. You must also be careful to include all punctuation, such as parentheses, commas, semicolons, and quotes. If you set a value equivalent to the Communicator default value, the line will be removed when you start Communicator.

When you are done modifying the file, save changes then open Communicator to test your new settings. If you have multiple user profiles, changes must be made to each user profile's prefs.js in order to implement the changes for all users.
 


Browser Settings -- Mail and News Settings -- Java and JavaScript Settings -- Other Options

Browser Settings

Maximum Number of Simultaneous Connections

The maximum number of concurrent HTTP connections to a web server. Increasing the value will only speed page loading if there is sufficient bandwidth as available bandwidth is divided among the connections, and decreasing the value may degrade performance. Default is 4 (fine for most modem users), minimum is 1. There is no maximum, but there is a limit of 6 open connections per browser window.

user_pref("network.max_connections", 6);
 

Network TCP Buffer Size

The amount of RAM (in bytes) to use for the TCP buffer. Larger values mean more data but can saturate the system on faster networks. Default is 10240 (10K) and is also the minimum, maximum is 31744 (31K). Values outside the limits will be taken to mean whatever limit is closest; i.e. 65536 will be taken to mean 31744.

user_pref("network.tcpbufsize", 31744);

Network TCP Timeout

The time, in seconds, before a timeout error appears when attempting to contact a server or perform a DNS lookup. This value should not be changed unless the user is experiencing frequent timeout errors (if this is the case, network maintenance is probably needed). A value of 0 for this parameter will use the default.

user_pref("network.tcptimeout", 120);
 

DNS Cache Expiration Time

The time, in seconds, before a server's IP address is purged from local memory. Subsequent requests to the server will require another lookup against the DNS server. The default value is 900 seconds. Unless there is a specific need to change this preference, it should remain the default value - reducing the value may negatively impact performance and increasing the value may cause problems against server farms.

user_pref("network.dnsCacheExpiration", 1000);
 

Disable Automatic URL Completion

Disables automatic URL completion ("AutoComplete") when typing in the browser location toolbar. Remove the line below to restore the feature.

user_pref("network.enableUrlMatch", false); <
 

Specify a Custom Bookmark File Location

Allows the user profile's bookmark file to be located anywhere on the hard drive or network drive rather than in its default location in the user profile directory. The Communicator bookmark filename is bookmark.htm. Note the double-backslashes in the path example below - use \\ where you would normally use \ in the path. (This feature is available in the GUI in 4.02 and up.)

user_pref("browser.bookmark_location", "C:\\Netscape\\bookmark.htm");
 

Disable HTTP_REFERER Headers

Disables the HTTP_REFERER header sent to the destination web server when you click a link. Be aware that disabling this header may cause failures in some scripts and pages requiring authentication partly dependent on this header. Remove the line below to reenable the header.

user_pref("network.sendRefererHeader", false);
 

Disable Asynchronous DNS

Disables browser use of asynchronous DNS. Disabling this feature may negatively impact performance and users should only disable this if so instructed by a system administrator or are troubleshooting winsock problems. Remove the lines below to reenable Asynch DNS.

user_pref("network.use_async_dns", false);
user_pref("network.wfe.use_async_dns", false);
 

Cache HTML Pages Accessed via SSL

Allows HTML pages accessed over secure (SSL) HTTP connections to be stored in the local disk cache. While this may aid performance as the pages can be stored locally, enabling local SSL page caching can represent a security risk since the secure pages linger on the local system. The default for this is to not allow local SSL page caching, and to disallow it again, remove the line below.

user_pref("browser.cache.disk_cache_ssl", true);
 

Show Images After Loading

Forces the browser to load the entire image before displaying it in the window. Remove the line below to allow images to display while loading once again. Note that this parameter may not work in all configurations. A setting of false is not recommended on modem connections.

user_pref("browser.display_while_loading", false);
 

Check to See if Default Browser on Startup

Forces Communicator to determine whether it is the default browser on startup.

user_pref("browser.wfe.ignore_def_check", false);
 

Maximum Number of Characters for Personal Toolbar Items

(Communicator 4.06 and up only) Controls the maximum number of letters an item on the browser's Personal Toolbar can contain before the item's name is truncated. The default is 15 characters.

user_pref("browser.personal_toolbar_button.max_chars", 25);
 

Use the Guide Button Instead of the My Netscape Button

(Communicator 4.06 and up only) Communicator 4.06 and 4.5 introduce the My Netscape button on the Navigation Toolbar. If you prefer to use the old Guide button, insert the following line into prefs.js. Remove the line to bring back the My Netscape button.

user_pref("browser.chrome.useGuideButton", true);
 

Modify the Default Search Engine

Changes the default search engine called when you type ?{search keyword} on the location toolbar. Note that this does not affect the Search button on the main navigation toolbar. The target URL should complete a form submission - for example, the AltaVista URL is http://www.altavista.digital.com/cgi-bin/query?pg=q&what=web&q= where the value for q will be filled in by whatever text follows the ? input by the user on the location toolbar. The default value for this parameter is http://cgi.netscape.com/cgi-bin/url_search.cgi?search= which will randomly select a search engine for the value of ? on the toolbar.

user_pref("network.search.url", "http://search.yahoo.com/bin/search?p=");
  

For Netscape 4.0 - 4.7, it is possible to search by entering "? " in the URL box 
instead of a URL. You can set the search engine used in this case by directly editing the prefs 
file. This can be dangerous! See the section above for more details on editing the prefs.js file.

Before starting, quit any copies of Netscape that may be running.

For Windows: To edit the prefs file, use Notepad to load ...\Netscape\Users\{username}\prefs.js. 
("..." is probably the "Programs" folder.)

For Macintosh: To edit the prefs file, use SimpleText or equivalent to load ...
:preferences:netscape f:netscape preferences. ("..." is your system folder.)

For UNIX: Edit the file .netscape/preferences.js in your home directory.

Once you've loaded the preferences file, add the following line to the end of the file:
user_pref("network.search.url", "http://www.google.com/keyword/"); Google Search for example.

Don't forget to hit <enter> at the end of the line!

Options for Sorting Server Directory Listings

Controls the sorting of server directories, such as FTP directories. Default is 0 (display alphabetically), 1 is sort by file type, 2 is by file size, 3 is by date.

user_pref("network.file_sort_method", 3);
 

Mail and News Settings

Reply on Bottom

(Communicator 4.02 and up only) Allows you to by default reply after quoted text. Default is 1 (reply on top), 0 is reply on bottom. Note that Communicator 4.5x has this option in GUI preferences under Edit | Preferences | Mail & Newsgroups | Messages.

To set it to reply on the bottom, cut and paste the pref below into your prefs.js file. Backup the file before editing !!!

user_pref("mailnews.reply_on_top", 0);
 

Disable the Messenger Start Page

(Communicator 4.5 and up only) Disables the Messenger Start Page, which loads in the message (bottom) pane of Messenger once at the beginning of each session. Remove the line from prefs.js to restore the page once disabled. If you would rather change the URL accessed, see the next preference below.

user_pref("mailnews.start_page.enabled", false);
 

Change the Messenger Start Page

(Communicator 4.5 and up only) Changes the URL that the Messenger Start Page retrieves. By default it will load http://messenger.netscape.com/bookmark/4_5/messengerstart.html but any valid URL can be used. If you wish to disable it instead, see the above preference.

user_pref("mailnews.start_page.url", "http://home.netscape.com/");
 

Add Extra Lines after Quoted Text

(Communicator 4.02 and up only) Allows you to specify an amount of extra lines to add after quoted material. The value is the number of lines to add.

user_pref("mailnews.reply_with_extra_lines", 2);
 

Control Movement Across Multiple Mail Folders and Newsgroups

(Communicator 4.02 and up only) Controls the behavior when the user clicks the 'Next' button to go to the next mail folder or newsgroup containing unread messages. Default is 1 (ask for user confirmation). 0 will cross folders without asking and 2 will restrict the Next button to the current folder or group (so it cannot be used to go to the next folder or group containing unread messages).

user_pref("mailnews.nav_crosses_folders",  1);
 

Disable Threading by Matching Subject Lines

(Communicator 4.5b2 and up only) By default, Communicator 4.5 will cause messages with the same subjects, without leading Re:'s, to get threaded together. To disable this behavior and rely solely on the Message-ID and References message headers for threading, use the following preference. Please note that newsgroup .SNM files will need to be deleted (and then recreated by Netscape) for the change to be fully committed.

user_pref("mail.thread_without_re", false);
 

Disable Automatic Mail Download

(Communicator 4.5b1 and up only) Communicator 4.5 and up by default download new incoming mail messages (POP3) or message headers (IMAP). To disable this and revert to the behavior of Communicator 4.0x and earlier, which merely notifies users that there is new mail waiting on the server, add the following lines as needed. If using a POP3 server, use the first line; if using an IMAP server, use the bottom line.

user_pref("mail.pop3_gets_new_mail", false);
user_pref("mail.imap.new_mail_get_headers", false);
 

Give Nickname Matches Precedence in Name Completion

(Communicator 4.5 and up only) During name completion of a name or address while in the message composition window (see Pinpoint Addressing in 4.5's Help), give the nickname match precedence over all other matches. Setting this to true implies that an exact match on a nick name field (such as "John") during name completion will take precedence over any other match. You will see an exact match for the entry with the nick name "John" instead of <Multiple Matches> if you have other entries that start with "John".

user_pref("ldap_2.autoComplete.nicknameHasPrecedence", true);
 

Always Request Return Receipts

(Communicator 4.5 and up only) Requests return receipts for all outgoing messages, relieving the user of the need to select it on a per-message basis. Remove the line below to return to the default behavior (don't request one unless the user specifically requests it).

user_pref("mail.request.return_receipt_on", true);
 

Always Use Binary Encoding for Message Attachments

(Communicator 4.5 and up only) Forces base64 binary encoding for mail and news message attachments, which may solve some attachment file corruption problems. Remove the preference below to return to the default, where Communicator guesses at
quoted-printable vs. base64 based on the file contents.

user_pref("mail.file_attach_binary", true);
 

Use MS Word Custom Dictionary

(Communicator 4.04 and up only) Allows sharing of the MS Word custom dictionary to augment Communicator's spell checker. The value is the full path to the dictionary (the filename is custom.dic and is found in the Office directory). Adjust the path below as necessary for your system.

user_pref("SpellChecker.PersonalDictionary", "C:\\Office\\custom.dic");
 

Use X-Sender Mail/News Header

Adds a X-Sender header to outgoing messages. If authenticated SMTP is not used, Unverified will appear after the user's e-mail address. Default value is false. An example X-Sender header is: X-Sender: "Moi" <moi@myisp.net> (Unverified)

user_pref("mail.use_x_sender", true);
 

Specify a Custom Address Book Location

Allows the user profile's address book file to be located anywhere on the hard drive or network drive rather than in its default location in the user profile directory. The Communicator 4.0x address book filename is abook.nab. Note the double-backslashes in the path example below - use \\ where you would normally use \ in the path. If the display of this line below wraps to two lines, you must enter it into prefs.js on a single line. This preference may not work in Communicator 4.5 and should be used in 4.0-4.06 only.

user_pref("ldap_1.directory1.filename", "C:\\Netscape\\Users\\your_profile\\abook.nab");
 

MIME-Encode 8-bit Headers

Always encodes 8-bit headers (separate from encode 8-bit characters in the GUI). Use strongly discouraged except where necessary.

user_pref("mail.strictly_mime_headers", true);
 

Disable JavaScript in Mail and News

Disables interpretation of the JavaScript language in the Collabra (news) and Messenger (mail) components of Communicator. JavaScript will remain available to the web browser unless JavaScript is globally disabled in Edit | Preferences | Advanced in the GUI preferences. Remove the below line and be sure JavaScript is enabled in preferences to restore full JavaScript functionality. Please note that Communicator 4.5 has this option in the GUI at Edit | Preferences | Advanced.

user_pref("javascript.allow.mailnews", false);
 

Disable Address Book LDAP Capabilities

Disables LDAP (Lightweight Directory Access Protocol) features in the address book. Remove the line to restore functionality.

user_pref("mail.addr_book.ldap.disabled", true);
 

Send Charset Data to Server for IMAP Searches

Allows character set data to be sent to the IMAP server for a search. Only needed in limited international use where the IMAP server also supports this functionality.

user_pref("mailnews.force_ascii_search", false);
 

Specify IMAP SSL Port

Allows specification of a non-default SSL port for IMAP communications. Default is port 993.

user_pref("mail.imap.ssl_port", 994);
 

Disable Registry Lookup of Unknown MIME Types

When a message is encountered containing a MIME type that Communicator does not know how to handle, it will fall back on the Windows 95/NT registry to determine a default action for the MIME type. This will disable that lookup in mail and news. Remove the line to restore functionality.

user_pref("mailnews.autolookup_unknown_mime_types", false);
 

Add HTML Domains to Address Book

Adds domains to the list in Edit | HTML Domains in the Address Book. All recipients in these domains are considered to have a mail/news reader capable of reading HTML. Add additional domains as demonstrated below (Communicator defaults to the netscape.com and mcom.com domains). Please note that Communicator 4.5 and up allow addition of HTML via the GUI by clicking Edit | HTML Domains in the Address Book and clicking 'Add New Domain'.

user_pref("mail.htmldomains", "netscape.com,netscape.net,mcom.com,foo.com");
 

 Java and JavaScript Settings

Disable Security for Unsigned Java Applets

Disables Java security for applets. WARNING: Since this parameter completely disables Java security, it should be only used for local applet testing and should never be used over a network and the Internet. Remove the line to restore Java security.

user_pref("signed.applets.codebase_principal_support", true);
 

Lock Java User Capabilities Database

Prevents users from adding additional functionality to the capabilities database (signed.db) such as by accepting signed Java applets from the Internet. If needed in a controlled environment, it is recommended that the CCK be used to lock this preference.

user_pref("signed.applets.capabilitiesDB.lock_to_current", true);
 

Simulate Navigator 3.0x Behavior for Local Classes

Allows local Java classes in the classpath to have special privileges such as universal network connections and the ability to load Dynamic Link Libraries. Access to the file system is not permitted with this option - the Capabilities API must be used instead.

user_pref("signed.applets.local_classes_have_30_powers", true);

More information on Communicator Java options can be found in the http://developer.netscape.com/docs/technote/security/sectn3.html.
 

Automate Opening of the JavaScript Debug Console

(Communicator 4.06 and up only) Due to popular demand, beginning with 4.06 and 4.5 JavaScript errors by default no longer pop up a debug window. Instead, there is a warning in the status bar noting that the page contained JavaScript errors and informing the user to go to a URL of javascript: in order to get the debug window (this was the JavaScript type-in window in prior versions). If you prefer the debug window to appear whenever an error occurs, add this line to prefs.js:

user_pref("javascript.console.open_on_error", true);
 

Use the Old JavaScript Error Dialog Boxes

(Communicator 4.06 and up only) If you prefer to use the old JavaScript error dialog boxes (as they were in 4.05 and earlier), add the following line to prefs.js. Note that if this preference is set, any setting for javascript.console.open_on_error, described above, will be ignored.

user_pref("javascript.classic.error_alerts", true);

Additional information on changes between JavaScript 1.2 (used in Communicator 4.0-4.05) and JavaScript 1.3 (used in 4.06, 4.5 and up) can be found on the http://developer.netscape.com/docs/manuals/communicator/jsref/js13.html, the Netscape Developer Site.


Other Options and Locking Preferences

Disable Roaming Access Options in Preferences

(Communicator 4.5b2 and up only) Prevents the 'Roaming Access' tree of options from appearing in the GUI preferences list when the user clicks Edit | Preferences. Remove the line to reenable the preferences.

user_pref("li.ui.enabled", false);
 

Disable HTTP MOVE Requirement for Roaming Access

(Communicator 4.5 and up only) If using HTTP Roaming Access against a web server that does not have the HTTP MOVE command implemented, such as a non-Netscape Enterprise Server, you will need to set the following preference. The MOVE command is used in 4.5 to prevent rare instances of file corruption or truncation on the server side if a transaction is cancelled or interrupted, but the simple PUT method, which is what the below preference sets, will work with a greater number of servers.

user_pref("li.server.http.useSimplePut", true);
 

Control Time Interval Between nsreg.dat Compactions

(Communicator 4.5b2 and up only) Controls the period of time between compression/updates of the Netscape Client Registry (...\%WINDIR%\nsreg.dat). The units for this preference are in days; the default is 60 days.

user_pref("autoupdate.regpack_interval", 30);

Please note that the above options can be set by any user able to modify prefs.js. If you operate in an environment that requires preferences to be locked in a certain state, you should consider the CCK, which allows you to lock both GUI preferences and those above plus several others. The CCK also allows you to universally set and/or lock preferences in all users' Communicators, eliminating the need to modify each and every prefs.js.

Netscape's DevEdge site provides a nearly http://developer.netscape.com/docs/manuals/deploymt/jsprefs.htm, a full list of Communicator preferences though it is not always kept current and mixes in preferences only available via the CCK. You can get a full list of your own preference settings by going to a URL of about:config in the browser.

Command Line Options are detailed on the http://developer.netscape.com/docs/manuals/deploymt/options.htm, Netscape Developer Site.

Netscape also has a number of undocumented functions, some useful, some fun. The following keystrokes are available in the browser window:

CTRL-ALT-T  Show the current state of HTTP connections (monitor progress of a loading page at protocol level).
CTRL-ALT-S  Hide/Show the browser status bar.
CTRL-ALT-F  Go to the http://home.netscape.com/fishcam/fishcam.html, Fishcam.

Additionally there are a number of about: functions which are mainly internal URLs (such as about:, about:javalogo, and about:license) while others link to developers' pages or are http://www.eeggs.com/, Easter Eggs (such as about:mozilla).

Other options, such as HTTP_USER_AGENT/X-Mailer header customization, logo image ("throbber") alteration, additions to dropdown buttons, and "about text" are only available in the CCK and cannot be set from the prefs.js file.

A free but more limited customization tool, the http://home.netscape.com/partners/distribution/custom/members.html, Client Customization Kit, is also available from Netscape.

Kevin Hecht

Visit the Main UFAQ Page for other Tips, Tricks and Setup Examples

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