When you say "When I go to the next tab" how are you doing that? For example:

• opening a new tab and expecting the Firefox new tab page (or a blank page) but get the other page instead
• the other tab is already open so you're clicking it on the tab bar
• clicking a link on your home page, and it is redirected
• doing a search from your home page and clicking a link in the search results

If it's that first one -- new tab page hijacked -- this could be caused by an add-on or by a hack in the Firefox program folder.

To investigate a possible add-on, you can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then cast a critical eye over the list on the right side. All extensions displayed here are optional. If in doubt, disable.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

You also could test in Firefox's Safe Mode. In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement? (More info: Diagnose Firefox issues using Troubleshoot Mode)