By default Firefox 4 betas are installed in a different location than release versions of Firefox. If you decide to use multiple versions of Firefox, make sure you install Firefox 3.6.* and Firefox 4 beta in different locations, you can use the custom installation option to choose where Firefox is installed. There is no guarantee that using an earlier user agent string will work, there may be changes in Firefox 4 that prevents the site from working. For the preference value, use a user agent sting from an older version of Firefox such as the one below.Right-click somewhere on that page and choose New > String.

Accept the warning message that appears, and this will bring up a list of preferences.Type about:config into the location bar and press enter.If you want to change the user agent string do the following: Personally I would not try this, instead I have multiple versions of Firefox installed, each with their own profile (location where user data is stored), and will switch to Firefox 3.6.* when required. This can cause issues with other sites which could end up reporting an incompatible browser if it was looking for Firefox 4. The application may be searching your user agent string to detect the version of Firefox, you could change your user agent string to make it appear that you are using an older version of Firefox.

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