see this might help http://mzl.la/1Sdozli

edit ~J99 Note that short link is for the help article

• Startup, home page, tabs, and download settings

Since you not running an up-to-date version of Firefox, your new tab setting has probably been modified by a third party program.

To remove this page as your new tab page, please do the following:

1. Enter about:config in the Firefox address bar
2. Click the I'll be careful, I promise! button
3. Locate the browser.newtab.url string
4. Change the value to the URL that you want to use as your new tab page or change it to about:newtab for the default new tab page

Note: Mozilla has discontinued this setting in the newer versions of Firefox for security purposes. This prevents issues of this nature from occurring.

Please update Firefox see

• Update Firefox to the latest release

P.S. And also see Troubleshoot Firefox issues caused by malware