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"invalid http request header" returned on all types of websites, not just yahoo, including search results and directly input web address.


I've been using Mozilla on my current laptop for a couple years now. However, recently, Mozilla has been returning a white page with the words "invalid http request header" at the top. If I hit the "back" button, it will reload and successfully load the intended page. This is not limited to any yahoo site. Whether I'm clicking on google search results or directly navigating to a site, I get this message and white page on about half the websites I try to visit. In fact, this website returned the same words. It's getting so frustrating that I'm going to go back to IE if I can't fix this.

Additional System Details

Sites Affected


Installed Plug-ins

  • npmnqmp 989898989877
  • np-mswmp
  • NPRuntime Script Plug-in Library for Java(TM) Deploy
  • Adobe PDF Plug-In For Firefox and Netscape "9.3.2"
  • The QuickTime Plugin allows you to view a wide variety of multimedia content in Web pages. For more information, visit the QuickTime Web site.
  • Default Plug-in
  • Shockwave Flash 10.1 r53
  • Adobe Shockwave for Director Netscape plug-in, version 11.5
  • iTunes Detector Plug-in
  • GEPlugin
  • 4.0.50524.0
  • Windows Presentation Foundation (WPF) plug-in for Mozilla browsers
  • Google Updater pluginhttp://pack.google.com/
  • Google Update
  • Unity Player 2.5.4b3
  • Java(TM) Platform SE binary
  • Next Generation Java Plug-in 1.6.0_19 for Mozilla browsers


  • User Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv: Gecko/20100722 Firefox/3.6.8 GTB7.1 (.NET CLR 3.5.30729)

More Information

  • Top 10 Contributor
  • Moderator
10779 solutions 97004 answers

Clear the cache and the cookies from sites that cause problems.

  • "Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"
  • "Remove the Cookies" from sites causing problems: Tools > Options > Privacy > Cookies: "Show Cookies"

If clearing the cookies doesn't help then it is possible that the file cookies.sqlite that stores the cookies is corrupted.
You can rename (or delete) cookies.sqlite and cookies.txt, if they exist, in the Profile Folder in case cookies.sqlite got corrupted.

See Fix login issues on websites that require a username and password (Remove corrupt cookies file)
See also http://kb.mozillazine.org/Websites_report_cookies_are_disabled (Other Solutions)