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

You do not need a Javascript code for that...
I think you mean the placeholder attribute. Here is the code:

The default text will be grey-ish and when clicked, it will dissapear!