Forms and Validation
Form validation is something you must do on your web server to ensure that you receive the data that is required and to remove, as much as possible, any vulnerabilities to hacking or the possibility of your server being compromised, as well as the data on it. However, it is very helpful to your users if you also provide validation directly in the browser.
For example, it can be particularly helpful to provide extra assistance when a user is filling in a form to save it from having to be re-presented to them if it fails validation at the server. It also cuts down on your bandwidth usage and keeps the optimum number ...