UAControl is a Firefox extension which provide users with options to change the user agent strings contained in HTTP header. Since the hosting server of the website you visit accesses User Agent string to know about the your browser along with other system-related details, you may want to change user agent string for specific web sites/domains which offers more features and functionality with preferred browsers, for e.g, Microsoft online services provide extra features to IE users only. UAControl lets you change the UA string on the fly, all you need is to specify custom User Agent string for specific domain.
Once installed, the main configuration window can be accessed from Tool menu and from Addons manager. You can start off with adding domains right away, with options to use the normal/default UA, or send the custom UA string in HTTP header. An option to block UA is also provided to block the sending of UA string.
At the lower part of the configuration window, you can define default UA strings for all websites which are not added in the list. The extension can be largely used for all UA sniffing websites which provide functions and features depending upon the browser and system information.
It works on Firefox 3.6 and higher versions.
UAControl Extension for Firefox