Make sure that you allow pages to choose their colors and that you haven't enabled High Contrast in the Accessibility settings.

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

See also:

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

nope didn't work it is the same in other browsers

Can you attach a screenshot?

• http://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

Use a compressed image type like PNG or JPG to save the screenshot.

Did you check the Accessibility settings in Windows?

• http://windows.microsoft.com/en-US/Windows7/Make-the-computer-easier-to-see-optimize-visual-display
• http://windows.microsoft.com/en-US/windows7/Getting-the-best-display-on-your-monitor

here it is

Looks that the CSS files are missing.

Did you try Safe mode?

• Help > Restart with Add-ons Disabled

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

See also:

• https://support.mozilla.org/kb/Websites+look+wrong
• http://kb.mozillazine.org/Websites_look_wrong