1. IE8's getElementById only supports id, not name
For example: <input type=text name=txt1>
Used in IE8: var obj = document.getElementById(txt1);
At this time obj will be equal to null
2. The <button> tag in IE8 will submit the Form by default, because the type of IE8's <button> tag is submitted by default.
So either set type=button, or return false when setting onclick;