After reading your post and second response,
I would bet you've been zapped by a
"browser helper object" which is "adding" links
to pages when you view them via a hidden redirect.
( and I would further suspect they are links to porn sites. )
You will find the entries in your registry and also find that
there has been a dll file added to your computer named
iehelp.dll
Download and run a copy of SpybotSD http://www.safer-networking.org/
it's free.
What do you mean?
1. The text of your webpages has been changed by someone
else.
2. Some other sites make links to your site.
-> You can't do anything against this. That's just the
way the www works...