New Features and Fixes

Browser

* 1.8 Alpha1 includes keyboard accessibility for the Mozilla Help window and improved keyboard accessibility for the Linux installer.
* Find in This Page now also searches inside textarea and text input boxes.
* Basic FTP upload UI has been added to Mozilla.
* Intellimouse Explorer Backwards and Forwards buttons are now supported on Linux.
* "Close Other Tabs" now has a confirmation dialog similar to closing a browser window with multiple tabs open.

Mail

* Mozilla 1.8 Alpha1 has UI for multiple identity support.
* Junk-mail filtering accuracy has been further improved.
* Users now have an option to mark incoming junk mail as read.
* Preferred mail format (plain text or HTML) is collected and remembered in the Personal Address Book.
* The Mail window menus have been adjusted to improve usability and resizing the mail window no longer resizes the folderpane.
* News now supports displaying the size column in KB or in Lines (via a hidden pref).
* Server wide news filters have been implemented.
* Addressbook auto-completion has been improved.
* 1.8a1 fixes an issue with listboxes that caused mail to display multiple attachments incorrectly. Additionally, mail sorting scrolls to keep the currently selected message in view.

Under the Hood

* Mozilla now has support for CSS2 quotes.
* The XUL Tree widget has undergone significant changes. You read more about that here
* The number of cookies Mozilla will hold has been dramatically increased and a hidden pref added for the few users who need even more.