Hello,

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• On Windows you can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac you can open Firefox 4.0+ in Safe Mode by holding the option key while starting Firefox.
• On Linux you can open Firefox 4.0+ in Safe Mode by quitting Firefox and then going to your Terminal and running: firefox -safe-mode (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

Thank you.

Thank you for your reply. Safe mode didn't helped. I tried Midori browser, but it's the same, also my android phone is doing the same on my home network, but not on mobile network, so I thought of it's caused by router settings. I tried to connect my pc directly to the ethernet, but there was something wrong with recognizing the connection and I have no access to WAN, LAN only. The stragest thing is that my sisters Windows Phone and Windows laptop can display these pages correctly. Please advise me something what can be wrong in router settings, I have it just a few days, it is TP-Link TL-WR740N.

Make sure that you haven't enabled a High Contrast theme in the Accessibility settings.

Make sure that you allow pages to choose their own colors.

• Edit > Preferences > Content : Fonts & Colors > Colors : [X] "Allow pages to choose their own colors, instead of my selections above"

Note that these settings affect background images.

See also:

• http://kb.mozillazine.org/Website_colors_are_wrong

Everthing was set right, system and Firefox are fresh installs so it isn't probably caused by Firefox settings. I thing there is something wrong with router settings, because it simmilar on my android phone when on home WiFi. Strenge is that on Windows Phone and Windows laptop everthing goes well.