It's not malware, as varjak paw has already indicated. It sounds like some sites you have been visiting have been somehow made to be carriers of a malicious JavaScript that redirects you to this site. That could be through malicious ads inserted in the site, it could be through hacking of the site, or it could be something else altogether.
You could try installing something like AdBlock or GlimmerBlocker, but those would only be effective if the script is part of an ad. You should also report the problem to the site(s) causing the problem, if they are legit sites, or avoid them if they are not unquestionably legit.
Edit: you could also try out JavaScript Blocker, which should help you block JavaScripts from running on certain sites.