form validation

The typical response you'll find based on your post is use a search engine such as Google to look for online tutorials. There are a lot of sites out there with basic information about JavaScript. For me, I always prefer a good book, text editor, and browser when practicing/learning JavaScript.

If you want some detailed help on this forum, the best approach is to provide more detailed information about the help you need by uploading sample, relevant code.

I agree with JorgeM.Until you provide your specific requirement,it is pointless to tell you appropriate book or site.
As if your site is using HTML5 then you can directly do validation using pattern attribute,required attribute that is introduced in HTML5.Check here the basic attributes added in HTML5 by w3.There are many new tags introduced by W3 like <input type="tel"> and so on,which signifies specific type of data.

If you want to use javascript then you can refer to http://eisabainyo.net/weblog/2009/04/30/10-examples-of-basic-input-validation-in-javascript/ / http://www.tizag.com/javascriptT/javascriptform.phpwhich specifies how you can do validation on javascript using regular expression in javascript,based on length and based on certain criterion.

ok i want to validate 3 forms
a sign in form
a registration form and a feedback form

the sign in form has
an email field
and a password field
a submit button

the registration form
has these fields
first name
last name
email
password
repeat password
three select boxes for the date (DD,MM,YY)
and a submit button

the feed back form
has
an email
subject
message
submit button