this method performs a case-insensitive match on both the ID and NAME attributes, which might produce unexpected results
We may NOT see any problem with this method as long as the ID and Name attributes of the controls on the webpage are same (which is the case most of the time). But, when values of these attributes are different e.g. while using a Master Page which mangles ID attributes by appending "_" and Name attribute using "$", getElementById in IE 7.0 might produce unexpected results. Read more about this bug here.