Website hijacking - escape & prevention

First off check whether your website is a victim of the famous 302 hijacking.

How to check
Go to google.com and type the keywords which your website is famous for or just copy & paste some header phrases from your website.
In the results if you spot other sites showing your web page content and your original content showing at the last 4-5 pages of google SERPS then your website has been hijacked.
But why? Because Google thinks that your website content is duplicating with the hijacker's and your website becomes penalized.
The other possibility for being put in the supplemental results is to have not well formatted content or such that shows duplicates in front of the search engines. So certain steps need to be followed in order to regain your SERP(position in the search engine index).

302 Hijacking prevention
Install at the very beginning of your web page the <base>HTML tag.
How:
just below the tag type:
<base href="http://www.yourwebsite.com">
This will point search engines that the content is going from your website and your website is the only authentic content source.

Then check whether you are using www or non-www URLs and convert your website to using non-www. Just type in your browser:
http://www.yourwebsite.com and http://yourwebsite.com
if your browser URL address remains the same then you are showing 2 exactly the same versions(with and without the preceding www) of your website to the search engines, this will not only lower your PageRank but is also considered as a spam. Do the same check for:
http://www.yourwebsite.com and http://www.yourwebsite.com/index.php or http://www.yourwebsite.com/index.html
Solution: You can use robots.txt, header meta tags(content="noindex") or in Apache driven server to modify .htaccess file rewrite rules to correct this problem.

Next run a simple search query:
site:http://www.yourwebsite.com
If you see only a few pages from your website being properly indexed(having proper title and description) and too many identical supplemental results ie. results with different title and same(repeated) description then part of your website resides in the supplemental index. This time the crawler thinks that you have a duplicate content in terms of repeated/same header meta information such as META description, META keywords and META title or their complete absence.
Solution: Go ahead and install or fix those appropriate META tags but beware not to overdo. In the next crawl your website pages will reappear again in the primary index of the search engine.

Removing impolite web hijackers from google search results
How?
First find out bad URL that is stealing your content.
Go to http://www.seoconsultants.com/tools/headers.asp and type the URL of the hijacker website. Execute the query. In the results if you find header status 302 then this website URL is stealing your content.

Then go to Google's removal page:
services.google.com:8882/urlconsole/controller
If you have found several hijackers then open the same amount of removal pages and type there their addresses.
Do not execute the removal query yet.
Next edit your website and put in the head section the tag <meta content="robots" content="noindex" >
After this execute google removal page and then return your normal robots tags to content="index".

You are ready. In the Google's removal queue you'll see the hijackers URLs and in the next crawl your website will again gain its popularity.

Cheers.