It's not your system, It's Mozilla changing the home page.

Okay, thanks. Thing is though that on my laptop that has Windows Vista as the operating system, no yellow on the opening page of Firefox and I uninstalled/reinstalled the browser today so I know it's the latest version. Just needs time to catch up or is the yellow colour specific to certain operating systems only?

A LOT of other users have been complaining about what Mozilla has been doing. Many have chosen to not use about:home Some even use an add-on to create a home page they can set up.

See my second reply here:

• [/questions/1038807#answer-670671] Who took a pee on Foxfire Start page; how get rid of yellow color?

Mozilla shows snippets on the about:home page to run different campaigns and that changes regularly.

If you prefer not to see snippets on the about:home page or if there are problems with a snippet then you can set the browser.aboutHomeSnippets.updateUrl pref to an empty string on the about:config page. Delete the storage\persistent\moz-safe-about+home folder in the Firefox profile folder with Firefox closed ("3-bar" Firefox menu button > Exit/Quit) to remove snippets stored in IndexedDB and make Firefox use a default snippet set. You can reset the browser.aboutHomeSnippets.updateUrl pref via the right-click context menu to the default value to re-enable the snippets and make Firefox recreate the moz-safe-about+home folder. Close and restart Firefox after changing the value of the browser.aboutHomeSnippets.updateUrl pref.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

You can use this button to go to the currently used Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)