Ah, if only we were all master spellers... . Since even the best of us get rushed at times or mistype words here and there, here are some alternatives for us all.
If you use Mozilla's
FireFox (available for free download from
www.mozilla.com) you can turn on spell checking from
Tools >
Options >
Advanced >
General, then select the box for
Check my spellings as I type and click on
OK. That's all. The in-line spell checker will underline unknown words in red. To see correct or alternative spellings or to add an unrecognized word, simply right-click on the mouse and make a selection. For example, the word "okay" is not recognized but can be added.
What about
Internet Explorer? It does not have an in-line spell checker. But there are free (for personal use) or inexpensive spell checkers that can be used as "add-ons" to IE. Rather than list them here, you can find several if you make an internet search using these 4 key words: "Internet Explorer" "spell checker".
My search results indicate Safari supports a built-in spell checker. To check for spelling or have Safari check the spelling as you type, simply go to
Edit >
Spelling and then choose the option you would like.
The above information covers spell checkers. Grammar and context is a related but different matter. If you type "an" when you meant "and", or "then" when you meant "than", or "hips" when you meant "hits", well, there are still some things left for you the author to proofread.

Or prepare your posts in a separate word processor which has those bells and whistles.