But there is a simple way in which you can overcome this problem using a simple solution in Firefox. All you have to do is select the text and right click anywhere on the page. Once you have done that you will see a hidden option View Selection Source. Once you click on this option you will see the actual HTML content that is used for displaying the selected content.
Now you can use this method and view the html source for any website even though if uses AJAX. I find this very useful when I create AJAX based sites and want to see if the html layout is proper.
If you are viewing a site but still cannot see the actual source just right near the content. If you see a additional context menu called This Frame it means that the content you are viewing is in a frame. Just go to the This Frame context menu and select any of the options that is provided.
Download Firebug for Firefox