Google is your friend: be nice and visit him often. He can find information a lot faster than post it here...
A simple search
using your subject as the search topic found 27,000 hits:
Google[
^]
The top one is from MSDN:
How to: Add a Watermark to a TextBox[
^]
In future, try to do at least basic research yourself, and not waste your time, or ours.