I shamefully admit to using reference.com for the thesaurus feature when writing papers. It appears that the site, which is owned by Ask.com is completely broken and only serves ads at this moment. So if you’re looking for a definition or synonym, you better look elsewhere, because reference.com is only going to give results offering 10% off or a free trial of whatever it is you’re looking up.

More examples: website
broken

UPDATE (Dec 3rd): it looks like this has been fixed