Reset Firefox
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[*] Click the

https://support.cdn.mozilla.net/media/uploads/gallery/images/2014-01-10-13-08-08-f52b8c.png" alt="" /> and then on Help

.
[*] From the Help menu, choose Information to troubleshoot. If you can not access the Help menu, type
about: support in the address bar to display the page
problems .
[*] In the upper right corner of the Troubleshooting Information page, click the Reset Firefox button. [Img]
https://support.cdn.mozilla.net/media/uploads/gallery/images/2014-12 -18-03-21-44-c81e72.png [/img]
[*] To continue, click Reset Firefox in the confirmation window that opens.
[*] Firefox will be closed in order to be restored. When finished, you will be presented with a window with all the information that has been imported. Click Finish and Firefox will reopen.
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After that I recommend installing the ABP plugin