Nope, just how you see other people's posts. If you want to change how people see your posts, you can use the font controls in the rich text editor (bold, underline, etc.)
Usually changing fonts for browsing is done on you Operating System (like Windows XP or 7) or at the browser level (Firefox or Chrome).
Maybe try these: http://www.computerhope.com/issues/ch000779.htm
http://www.wikihow.com/Change-the-Font-Size-in-a-Browser