Ok, here is the deal, I am not a lawyer, or an expert in law in any way. If you want full legal help, I would suggest that you do speak with a lawyer.
What you want to do is make yourself familiar witht eh OGL licence. In the section 15 you want to designate what is Open Game Content. (Since all of the spells are derived from the SRD, you have to make all that open) There maybe other materials that you would like to make OGC, but since I have no idea on what that would be you ill have to make that call yourself.
As a suggestion, you could make a readme.txt file with the Open Gaming Licence in it or you could include it in your html file, as long as it was easy to find. I might even suggest both.
If you have Tome of Horrors, there is a OGL primer in the back of it, I suggest that you take a look at it.
also check here.
http://www.opengamingfoundation.org/d20.html
and here
http://www.wizards.com/D20/main.asp?x=welcome,3