body { 
  font-family: Verdana,Arial,sans-serif; font-size:10pt; font-weight:bold; color:#000;
  background-color: #FFFFCC;
     }
td   {
  font-family: Verdana,Arial,sans-serif; font-size:10pt; color:#000;
  background-color: #FFFFCC;
     }     
  
  
  
  
  
  
<input type="text" name="txtPostalCode" 
onKeypress="if(event.keyCode < 45 || event.keyCode > 57) { 
event.returnValue = false; 
} else {
if(event.which < 45 || event.which > 57) return false;
}">