Javascript Validation

I have been a webdeveloper since a while now however recently I came across an issue with a client's website I was working on, the issue was that I was having invalid submissions that were not possible considering that I had validation over the form submission like authenticating the correctness of URL. The question I finally asked was that was javascript validation enough? And to my surprise disabling (and hence) by passing javascript is fairly simple, once the user disables javascript then he can submit anything and bypass all your javascript checks so make sure you always have validation both at client side as well as server end.

Happy coding.