function letternumber(e)
{
var key;
var keychar;
if (window.event)
key = window.event.keyCode;
else if (e)
key = e.which;
else
return true;
keychar = String.fromCharCode(key);
keychar = keychar.toLowerCase();
// control keys
if ((key==null) || (key==0) || (key==8) || 
(key==9) || (key==13) || (key==27) )
return true;
// alphas and numbers
else if ((("abcdefghijklmnopqrstuvwxyz0123456789@_-./").indexOf(keychar) > -1))
return true;
else
return false;
}