Usually some badly crafted JS that keep accumulating huge chunks of memory.
I blacklisted Tutorialspoint earlier. Another site with very bad memory management. Perhaps they have fixed it now though. Have not been there for a long time.
@FaheemMitha Yes. It's insanity on stereoids. I run some browser-games that use a lot, like 1G+, but can be defended to a higher degree. For a site delivering text articles however … it's just /o\ Funny enough most of the sites I have come across with bad memory leaks are for the most part "tech sites".