To enable html in your posts it is very very simple. I have allowed HTML from the site, but you also must turn it on.
Here is the step-by-step
1- Click the profile button found in the bar right below the site's manip.
2-Click the preferences link found above all of the text fields, but below the bar mentioned in step one.
3-Scroll down till you see " Always allow HTML : YES OR NO " You need to move the dot to the yes side. Then click save found in the bottom of the page.
Now your posts can have html in them!
If you have any questions feel free to pm me