文本框输入----数字判断

http://hi.baidu.com/flair988/item/2a26dcf634d6bf4a922af2f4

<input type="text" name="url" onkeypress="IsNum(event)">

<script>

function IsNum(e) {

           var k = window.event ? e.keyCode : e.which;

           if (((k >= 48) && (k <= 57)) || k == 8 || k == 0) {

           } else {

               if (window.event) {

                   window.event.returnValue = false;

               }

               else {

                   e.preventDefault(); //for firefox

               }

           }

}

</script>