This post is completely for developers, unless and until if you are really keen to know what User agent is and why does one has to switch it ? So you started developing and website/blog and it has a capability to do some extra stuff for different type of browsers. For instance if your website is going to open in iPhone, then you might want to show glossy stuff with all the bells & whistles on its place, whereas when it opens in a normal symbian or opera browser, you ought to show a simple sleek small sized pages in the mobile browser.
But it becomes practically impossible to have all the gadgets in one place and do the testing. So to overcome that problem you can install User Agent Switcher , a very useful addon for Mozilla Firefox. After installing this addon you can switch to standard user agent which is already there. But if you want anything specific, then you can always add your own user agent with all the specification on its place.
Hope this addon helps you in development work by making it easy to use one browser instead of using multiple.
Stay Digified !!