If you have more then one browser like IE, FF, Safari or Chrome then windows or any other operating system needs to know which browser to use by default?
This article will show you the step how to set firefox as default browser.From the menu bar select on Tools → Options and it will open following screen
Figure 1As per above figure select advance option from options then go to General tab.
In the system defaults panel there is a button with captions Check Now Just click it and it will ask for the confirmation, click on OK button and you are done. You can see confirmation dialog box like Figure 2