Warning: Visiting this site may harm your computer!

Solution 1:

you got blacklisted for a reason. check your site really well:

• get tool like fiddler, open your page in web browser and make sure requests sent from your computer go just to your site [ or trusted 3rd party sites ]
• open all index.html/php in text editor, turn on wrapping and search for rogue javascript / html code.
• check content of .htaccess files and make sure they do not contain any malicious rewrite / redirection rules

there is a plague of programs stealing passwords from ftp clients and uploading rough html / javascript / .htaccess files.

or maybe you just got hacked / are victim of js/html injection to your cms.

Solution 2:

I actually notified a friend of mine the other day that her site got blacklisted the same way. I looked through the source code on her index and she had shady looking obfuscated javascript in her head tag. I think this is generally the reason this happens. Someone compromised your website and you need to find where the problem is as soon as possible.