For example, if you are going to send an email confirmation letter, the email address should be included in the form fields, and it should be an email address that works.There are two ways to validate your forms: The basic premise of creating form validation is to look for the names of form elements that are required, and if they are empty, display an error message.If you use the following script and Perl source you will know how to validate an entire form at once, displaying a series of error messages that your reader can then go back and fix.In the head portion of your HTML, you should create a script to do the form validation: See the validation script in action.
A good place to find CGI programs is The CGI Resource Index. You can see if your Web server has one available for your use, and find out from them how to use it in your HTML form code.
While HTML5 form validation is typically about missing or invalid text inputs, there are other form element types that also require attention. Suppose you have a form on your website that at the bottom asks people to "accept the Terms and Conditions" or something similar.
Basically you don't want the form to be submitted unless this is checked.
This validator checks the markup validity of Web documents in HTML, XHTML, SMIL, Math ML, etc.
If you wish to validate specific content such as RSS/Atom feeds or CSS stylesheets, Mobile OK content, or to find broken links, there are other validators and tools available.