Enhancing a text box with the TextBoxWatermarkExtender
TextBoxWatermark is an ASP.NET AJAX extender that can be attached to an ASP.NET TextBox control to get "watermark" behavior. When a watermarked TextBox is empty, it displays a message to the user with a custom CSS style. Once the user has typed some text into the TextBox, the watermarked appearance goes away. The typical purpose of a watermark is to provide more information to the user about the TextBox itself without cluttering up the rest of the page.
The control above is initialized with this code. The italic properties are optional:
WatermarkText="Type First Name Here"
TargetControlID - The ID of the TextBox to operate on
WatermarkText - The text to show when the control has no value
WatermarkCssClass - The CSS class to apply to the TextBox when it has no value (e.g. the watermark text is shown).