Visual Studio allows you to set default browser to debug your ASP.Net (and Silverlight) application, this is helpful when you want to check/ debug your application in different browser.
To set default browser, right click on your aspx file and select “Browser With…”.
From the “Browse With” dialog box, select the Browser of your choice and click on “Set as Default” button. You can also set the size of the browser window from this dialog box.
Next time when you run application from Visual Studio, it will run on the browser you set as default. This is just for the Visual Studio, your system default browser setting will not be affected by this.