Textbox allow numeric only

function ChkNumeric()
{ //alert(event.keyCode);
if(((event.keyCode>=48) && (event.keyCode<=57) || (event.keyCode==9) || (event.keyCode==8) || (event.keyCode==13) || (event.keyCode==46)) || ((event.keyCode>=96) && (event.keyCode<=105)))
{
event.returnValue=true;
}
else
{
alert("Only Numerics Are Allowed")
event.returnValue=false;
}
}