// needs JavaScript1.2 and proper DOM support

if (document.getElementsByTagName) {
  addEvent(window, 'load', set_alternate_table, false);
}

function set_alternate_table() {
 var all_cells = document.getElementsByTagName('td');
 var l = all_cells.length;
 for (var i = 0; i < l; i++) {
   addEvent(all_cells[i], 'mouseover', hi_cell, false);
   addEvent(all_cells[i], 'mouseout', lo_cell, false);
 }
}

// climb up the tree to the supplied tag.
function ascendDOM(e, target) {
 while (e.nodeName.toLowerCase() != target && e.nodeName.toLowerCase() != 'html')
   e = e.parentNode;
 return (e.nodeName.toLowerCase() == 'html') ? null : e;
}

// turn on highlighting
function hi_cell(e) {
 var el;
 if (window.event && window.event.srcElement) el = window.event.srcElement;
 if (e && e.target) el = e.target;
 if (!el) return;

 el = ascendDOM(el, 'td');
 if (el == null) return;

 var parent_row = ascendDOM(el, 'tr');
 if (parent_row == null) return;

 var parent_table = ascendDOM(parent_row, 'table');
 if (parent_table == null) return;

 // row styling
 parent_row.className += ' hi';

 // column styling
 var ci = -1;
 for (var i = 0; i < parent_row.cells.length; i++) {
   if (el === parent_row.cells[i]) {
     ci = i;
   }
 }
 if (ci == -1) return; // this should never happen

 for (var i = 0; i < parent_table.rows.length; i++) {
   var cell = parent_table.rows[i].cells[ci];
   cell.className += ' hi';
 }
}

// turn off highlighting
function lo_cell(e) {
 var el;
 if (window.event && window.event.srcElement) el = window.event.srcElement;
 if (e && e.target) el = e.target;
 if (!el) return;

 el = ascendDOM(el, 'td');
 if (el == null) return;

 var parent_row = ascendDOM(el, 'tr');
 if (parent_row == null) return;

 var parent_table = ascendDOM(parent_row, 'table');
 if (parent_table == null) return;

 // row de-styling
 parent_row.className = parent_row.className.replace(/\b ?hi\b/, '');

 // column de-styling
 var ci = el.cellIndex;
 for (var i = 0; i < parent_table.rows.length; i++) {
   var cell = parent_table.rows[i].cells[ci];
   cell.className = cell.className.replace(/\b ?hi\b/, '');
 }
}

function addEvent(obj, evType, fn, useCapture){
if (obj.addEventListener){//DOM
  obj.addEventListener(evType, fn, useCapture);
  return true;
} else if (obj.attachEvent){//IE
  var r = obj.attachEvent('on'+evType, fn);
  return r;
} else {//IE5/Mac
  obj['on' + evType] = fn;
  //return false;
}
}