function clickButton(e, buttonid) {
    var bt = document.getElementById(buttonid);
    if (typeof bt == 'object') {

        var evtobj = window.event ? event : e //distinguish between IE's explicit event object (window.event) and Firefox's implicit.

        if (evtobj.keyCode == 13) {
            bt.click();
            return false;
        }
    }
}