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There's quite some buzz online about the Firefox OS. Here's how you can get your hands on trying out the FF OS without having to go through too much of trouble.
There's this "Firefox OS Simulator" addon available on FF Addons, which allows you to simulate FF ... 
Sometimes Firefox automatically switches to "Offline Mode" [Work Offline Mode] on trivial issues like a router reboot or a temporary DNS Error. The trouble is, FF fails to come back out of it even after the problem is resolved after a few minutes.
In Firefox's addressbar type ... 
My new laptop came with "AVG Secure Search" as the default engine and it was pretty annoying. Typing a query in the addressbar and hitting enter would throw up AVG's SERP. Here's how to change it:
Changing default Search Engine
In firefox's addressbar, type about:config
In the filter bar, ... 
Firefox 4 Beta 1 is out. And you can try it out here.
Whats new
Visual Changes : All menus merged to one single orange firefox button on top left; New position for Tabs.
Crash Protection for 3rd party plugins.
Switch to Tab in the AwesomeBar.
Full support for CSS3, HTML5
Indexed ... 
Firefox 3.6b1 is now available for download
Notable changes in 3.6 Beta vs. Firefox 3.5
Supports file-based Drag and Drop so you can Drag and Drop files from your desktop in the browser. Mixed with the File API (mentioned below) this can make for a very powerful set ...
Firefox shows two titlebars after update
Stop Firefox from automatically Scanning for Viruses
Lightning Fast Browsing Trick For Firefox and IE