Some browsers provide spell checking... that is when you see the red squiggly lines under words you type.
Chrome does it, Firefox also. There's a plug-in available for Internet Explorer (
http://www.iespell.com). Safari also supports it but it must be switched on (Edit / Spelling and Grammar -> Check Spelling as you type). It does not remember this setting between sessions, AFAIK.
The observant are right. We used to have server-based spell check (with the spell check link), but lost it a while back when I upgraded some server software. I didn't bother going through the motions trying to get it back given that most people can use one of the above solutions.
Peter