I began play with Visual Studio 2005 and discovered that Internet Explorer is used for debugging. In the past one could change the default browser before going to the file menu then to “Browse With” in Visual Studio however this seems to have changed. Here is a couple solutions I found out how to change your default browser in Visual Studio 2005.

Solution One

1. Go to File menu > New > Web Site.
2. Go to File menu > Browse With.
3. The “Browse With” dialog will appear, click on Add and then select your preferred browser.
4. Click on your preferred browser in the list and click on “Set as Default”.
5. Click on “Browse” or “Cancel”.

Solution Two

1. Left click on a aspx file in the “Solution Browser” and click “Browse With”.
2. The “Browse With” dialog will appear, click on Add and then select your preferred browser.
3. Click on your preferred browser in the list and click on “Set as Default”.
4. Click on “Browse” or “Cancel”.

Source: Changing your debug browser to Fire Fox in Visual Studio 2005