This WYSIWYG (What You See Is What You Get) editor is great if you don't know HTML. It lets you customize basic elements such as text, links and tables like if were using a word processor, so you can center and change size, color and fonts with ease. This is NOT for creating a layout, that is what the Profile Editor is for, this HTML editor is only for helping you customize the content you put on your profile.
To get the HTML code click the image in the second row of buttons! Copy and paste the code that appears in the pop-up window.