Are you sure that you didn't inadvertently set both as your homepages? See - How to set the homepage

Went to Options, General, Set Homepage, and there it was: the homepage I set and the Mozilla Firefox home page following it. Deleted the 2nd page and it only loads the page I set now. Thank you. Little problem but was frustrating.

How would I know that...setting anything on FF is very confusing and frustrating. Why can't we have a simple option that says set as home page rather than having to go through support pages that only tell one to see another and another etc. This is like reading tax law!

There is a simple option to set your homepage, which you can find by reading the correct support page - https://support.mozilla.org/en-US/kb/How%20to%20set%20the%20home%20page - or you can find it by exploring the Options in Firefox. [On Linux and MacOSX versions of Firefox, Options is called Preferences.]

The instructions are clear and easy to understand, however, it doesn't always work. I set my home page to www.google.com (only one tab opened up), clicked OK to save google as my home/start page. I closed all browsers, started FF and it worked. However, the next time I started FF it came back with the hooray, your ff is up to date. I also set my home page to my internal work site URL, same problem. I'm using version 23.0 I also tried going to google, and dragging the icon at the beginning of the URL to my home page icon. Still doesn't work. DOH