Disallow illegal characters in textbox

Hello This is all i need.. I have about 3 textboxes. I am in need of some code that can disallow illegal characters, or just characters i can choose from in a textbox. maybe when they click outside the box or something, a messegebox shows up, or they just cant type the letters in at all. Basically i dont want users being able to enter . or -, etc in a textbox. I also want code to limit the number of letters one can type in a textbox. hope this is clear enough, thanks! ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform php, html.