When you're too impatient to wait for a response on a forum thread, you write "bump 10char" to push it to the top of the forum so more peoplewill see it. The 10char part is to meet the requirement of some forums to have 10 characters in a post.
Original poster: What's your favorite Pokemon?
*Five seconds without a response*
Original poster: Bump 10char
New poster: Pikachu.
Original poster: Yay! A response!
10chars an abbreviation for "10 characters." It is used as a method of bypassing 10 character limits in forums when your post would have otherwise been too short.
It's now mostly a joke, however. Posters will be most likely seen just using the number and adding a humorously relevant/silly/sexual substitute for "chars", especially when their post is already above 10 characters.
Ruler of Lake Titicaca. Rumored to have a bunghole that gets very angry if it does not receive toilet paper. Cornholio the Great is often seen walking around with his shirt over his head and his hands in the air, chanting songs about his power, and his bunghole.
"I am Cornholio! You do not want to face the wrath of my bunghole, for I need TP!"
Butthead: Shut up, Beavis! (uh huh huh huh)
Beavis: Um, okay. (heh heh heh heh).