This is a very common usecase we see on stackoverflow, facebook, etc.
You often want to give the user some text to direct him on what to do, but you want the text to disappear the moment he clicks on it.
What is the easiest way to do that via JQuery? This seems like a fairly common use case
What I think you’re looking for is generally called a “watermark” – and you’re right, this is very common. There are a number of jQuery plugins available to do just what you’re asking.
For example: http://code.google.com/p/jquery-watermark/