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.
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 people will 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!
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.