$('input.asci_only').keypress( function(e) {
     if($.browser.msie)
         return isAsci(e.keyCode)
     else  
         return (e.keyCode) ? true : isAsci(e.charCode)
});
function isAsci(cCode){
     return /[a-zA-Z0-9@\.]/.test(String.fromCharCode(cCode))
}