<script type="text/javascript" charset="utf-8">
$(document).ready function CheckInput() {
   if ( ! checkID( document.Form1.ID.value ) )
      window.alert( "The ID is wrong" );
}
function checkID( id ) {
  tab = "ABCDEFGHJKLMNPQRSTUVXYWZIO"                     
  A1 = new Array (1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,3,3,3,3,3,3 );
  A2 = new Array (0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5 );
  Mx = new Array (9,8,7,6,5,4,3,2,1,1);
 
  if ( id.length != 10 ) return false;
  i = tab.indexOf( id.charAt(0) );
  if ( i == -1 ) return false;
  sum = A1[i] + A2[i]*9;
 
  for ( i=1; i<10; i++ ) {
    v = parseInt( id.charAt(i) );
    if ( isNaN(v) ) return false;
    sum = sum + v * Mx[i];
  }
  if ( sum % 10 != 0 ) return false;
  return true;
}
</script>

for ( i=1; i<10; i++ ) {
...
    sum = sum + v * Mx[i;
  }