rem: return e; 
add: return (e.nodeType == 1) ? e : null; 
context: function getAncestorByTagName(e, tagName) {  tagName = tagName.toLowerCase();  do {    e = e.parentNode;  } while ((e.nodeType == 1) && (e.tagName.toLowerCase() != tagName));  return e;}
meta: 2557	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/2557/3b7ebcf5ecf25055951f5338ef95ab9ebbcf0fa4/trac.js/buggy/htdocs/js/trac.js