How to create a label inside an <input> element?

Question

I would like to insert a descriptive text inside an input element that disappers when the user click on it.

I know it is a very common trick, but I do not know how to do

Answer 1

I've put together solutions proposed by @Cory Walker with the extensions from @Rafael and the one form @Tex witch was a bit complicated for me and came up with a solution that is hopefully

error-proof with javascript and CSS disabled.

It manipulates with the background-color of the form field to show/hide the label.

        Your name
        

View the script in action: http://mattr.co.uk/work/form_label.html