When does it come up? Home page? Newtab? Could you post the page's link?

You can open the about:config page via the location bar and search for prefs that refer to that Weather Channel site. You can reset user set (bold) prefs via the right-click context menu to the default value.

You can check the target line in the Firefox desktop shortcut (right-click: Properties) to make sure that nothing is appended after the path to the Firefox program.

Your System Details shows;

Installed Plug-ins

Shockwave Flash 14.0 r0 Shockwave Flash 13.0 r0

Having more than one version of a program may cause issues.

It could be the work of one of your add-ons, or even add / mal-ware. Look thru your add-ons list and make sure you know what each one is there for. Also, check the programs that are on your computer

Windows: Start > Control Panel > Uninstall Programs. Mac: Open the "Applications" folder Linux:

• Ubuntu Unity {web link}
• Xfce: Applications Menu category sections
• options depends on the package manager and the desktop environment

Go thru the list. If you find something that you don't know what it is, use a web search.

Troubleshoot Firefox Issues Caused By Malware {web link}