http://www.mozilla.org/releases/

* MathML is now enabled by default on those platforms that support it, including Windows and Unix. MathML is the W3C specification for describing mathematics on the web. To properly display MathML you need to install special math fonts that are not installed by default on most systems. If you are reading this with Mozilla 0.9.9, take a look at this MathML sample which should look fine without these fonts.
* The JavaScript debugger, (aka Venkman) can now profile JavaScript in web content and browser chrome. Select Profile->Collect Profile Data to start profiling, execute the script you'd like to profile, and select Profile->Save Profile Data As... to save it. Statistics are collected for every function executed while profiling is enabled, and include total, maximum, minimum, and average time spent executing the function, and total number of calls. Supported output formats are HTML, CSV, and plain text. Sample profile output is available here. Be sure to start the debugger before loading the scripts you're going to profile.
* Mozilla now supports TrueType fonts on Unix using the FreeType2 library. This works on all X servers with a TrueColor visual (ie: a 15/16/24/32 bit frame buffer). This is enabled on Linux i386, Solaris, HP-UX and some other Unixes. Read these directions on setting up TrueType support in Mozilla.
* Greatly improved View-> Page Info dialog.
* Mozilla now supports SOAP.
* You now have the option of installing plugins in your Mozilla user directory ($HOME/.mozilla/plugins on Unix). These plugins are loaded in addition to those in your Mozilla install directory.
* Mozilla has a new Page Setup dialog and the Print Preview window now has a toolbar.
* Mozilla on Microsoft Windows now has a full screen mode.
* Speed improvements for the Sparc Solaris build.
* The BeOS port now supports SSL and has gfx speed improvements.
* Mozilla has a new method for disabling popup and popunder windows. It is now possible to disable the JavaScript window.open() method when it is not called as a result of a mouse click. When the dom.disable_open_click_delay pref is set to a nonzero number, window.open will fail when called more than that number of milliseconds after a mouse click. Setting this pref (instructions here) should turn off pop-up and pop-under ads that use the onload handler of <img> tags to work around our previous window.open() filter. (Bug 92955)

user_pref("dom.disable_open_click_delay" , 1000);
* Mozilla's zlib library contins the fix for the zlib vulnerability. Note that some builds such as the Red Hat RPMs use the sytem zlib library and you will need to update this library separately. See the Red Hat Linux Errata Advisory.
* The recycled mail compose window was turned on by default which greatly improves new message and reply performance.
* A new mail notification appears in the Windows System tray.
* Mozilla now supports the use of socks proxies for mailnews. The value entered in prefs-> advanced-> proxies-> socks host will be used for this. You must ensure that this field is left blank unless you require a socks proxy. If that field contains an entry that is not actually a socks proxy, then you will receive an error about connection being refused to your mail server. If you use a socks proxy and want to read mail from a site that the socks proxy does not have access to (such as localhost), you need to manually exclude those site(s) from being proxied by adding it to the "no proxy for" pref.
* LDAP directories appear in the address book.
* The address book now has an advanced search dialog.
* IMAP Shared Folders is finished with the exception of being able to click on an imap url to subscribe to one.
* The delete key now toggles the deleted state for the IMAP delete model.
* Improvements to the MailNews UI when reading signed and encrypted S/Mime messages.