How to add to a textbox the red line (like bad spelling in Word)?

Question

How can we produce the effect of the red line under a bad spelling word like the image below :

alt text http://img505.imageshack.us/img505/7253/options285x395rg9.th.

Answer 1

use google's spellchecker

http://www.asp101.com/articles/jeremy/googlespell/default.asp