<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>Required Field</title> <SCRIPT> function checkRequired() { var num=document.card.cardnum.value; alert("your enter the value:"+num); document.card.cardnum.value=37; event.returnValue=false; } </SCRIPT> </head> <body> <form action="clear.html" name="card" id="card" onSubmit="checkRequired();"> Enter your name:<br> <input type="text" name="cardnum" size=10><br> <input type="submit"> </form> </body> </html>