Allow only digits, delete and backspace.

$('#selector').keydown(function(event) {
				if ( event.keyCode == 46 || event.keyCode == 8 || event.keyCode > 112 ) {
 
				} 
				else {
					if (event.keyCode < 95) {
						if (event.keyCode < 49 || event.keyCode > 57 ) {
							event.preventDefault();
						}
					} 	
					else {
						if (event.keyCode < 97 || event.keyCode > 105 ) {
							event.preventDefault();
						}
					}	
				}
 
			});