Depending on the operating system you use you may or may not have a spell check when you make your posts. I used to have it but not any longer, and since I'm not too internet savvy I have no idea how I got it in the first place or what happened to it since...
I agree with Jim, depends on your OS and what browser you're using. I use Chrome and I have the spell check that does the squigglies like asterisk mentioned. It's nice, it's a lot of trouble to use other kinds.
You can download Firefox Here http://www.mozilla.org/en-US/firefox/new/?utm_expid=65789850-8 It is less trouble free software then Explorer and has built in Spell Check whenever you use it. If you are not comfortable with that,you can use add-ons to Explorer 7 and 8 and they willl work fine. Here are a couple of those. http://www.iegallery.com/Addons/Details/11171 http://www.iegallery.com/Addons/Details/443