I try accessing Wikipedia; alas, however, the ask.com web site comes up rather than English or Simple English Wikipedia. Please help me!

Your issue may be caused by Malware. You can run and update the following free anti virus software:

1. Malwarebytes (Free version) - http://www.malwarebytes.org

2. Spybot Search & Destroy - http://www.safer-networking.org

3.Spyware Terminator - http://www.spywareterminator.com (Not all programs detect the same infection)

The downloads you suggested are taking too long to enter operation. I am really worried about my ability to access English and Simple English Wikipedia areas. I wanna access those because of highly important topics related to 18th Century! Other issues, along with malware, may be preventing me from getting to those areas without having redirection problems.

One of your add-ons might be the culprit too. Try running Firefox in Troubleshoot Firefox issues usingSafe Mode with all add-ons disabled.

If that solves the problem, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems  

and possiblyTroubleshoot issues with plugins like Flash or Java to fix common Firefox problem

In addition, there are a number of forums you can use to help get rid of your infection. These include:

   http://www.bleepingcomputer.com/forums/ 

   http://forums.spybot.info/ 

   http://www.spywarewarrior.com/index.php

You can use the SearchReset extension to reset some preferences to the default values.

• https://addons.mozilla.org/firefox/addon/searchreset/

Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).

If you do not keep changes after a restart or otherwise have problems with preferences, see:

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