<html> <head> <script type="text/javascript" src="js/jquery-1.3.2.js"></script> <script type="text/javascript"> $(document).ready(function(){ $('input').load(function(){ if($(this).height() > 100) { $(this).addClass('big'); } }); }); </script> </head> <body> <body> <input type="text" /> </body> </html>