Validation

Even though there are several new input types, without a doubt the biggest new feature is the built-in form validation HTML5 offers. Previously, you had to use server-side code like PHP or C# to check the contents of the submitted form and then return the page and display the errors to the user. Or you had to use some fancy JavaScript to check the contents of the data entered on the fly and tell the user whether there were any errors.

With HTML5, form validation is easy; you can provide inline validation and feedback for the users when they try to submit the form, which leads to forms being easier to complete and increases the chances of correct information being submitted. Of course, you will need some server-side code to actually process the form to its destination.