One of the many inside internet jokes, which consists of pictures of cute kittens, cats, and cats in funny poses, which then have captions in large (generally white) font taking up AT MINIMUM a fourth of the page. Misspellings and atrocious grammar are common, the most frequently used phrase is "I can haz cheezburger?" spelt a number of different, and all wrong, ways.
A large archive of photos, captions, and al manner of idiots who find them funny can be found at Icanhascheeseberger.com.
Did you see those lolcats? That one "haz a corm!" Ahahahahahaha!
September 23, 2008