HTML CODE
<input type="text" name="mobile" onkeypress="return isNumber(event)" />
JAVASCRIPT CODE
function isNumber(evt) {
evt = (evt) ? evt : window.event;
var charCode = (evt.which) ? evt.which : evt.keyCode;
if (charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
}
return true;
}
DEMO
Check this link http://jsfiddle.net/vetri/vsmju7xt/
