Want to keep menu always appear on the top, even if you scroll down the page ?

Just follow simple two steps process.

Form validation normally used to occur at the server, after the client had entered all the necessary data and then pressed the Submit button. If the data entered by a client is incorrect or is simply missing, the server would have to send all the data back to the client and request that the form be resubmitted with correct information. This is really a lengthy process which used to put a lot of burden on the server.

That expalins the client end form validation using Javascript.