So whenever I post I always see the button that says preview and have never known what it does. I've never actually pressed it because I'm to afraid that it will ruin my post and I've tried to preview before posting but it won't let me.

It’s a feature that allows you the chance to see what you write as it would look when posted, before you actually post it. I use it to make sure it looks the way I want and I haven’t messed up the coding somewhere. It’s also a great chance to proofread as it will look when posted.  I find I miss things in the text box that I only see when formatted as a post. :)

Ok.