Magic.
this^^ and I'm pretty sure when you go in through settings there is a preview button..."GawjussGracieex" wrote:
If you go onto your profile and click on edit themes (next to your profile pic), it updates the changes you're making automatically so you can see what it looks like. I don't think that applies for the background though, you'd have to save it first in order for it to update. I think a preview on the bio would be cool though!