document.onkeypress = function(e) {
    if (document.location.href.lastIndexOf("/Login.aspx") > 0) {
        var cPrefix = document.getElementById("ClientPrefix");
        var evt = e || window.event;
        var key = evt.which || evt.keyCode;

        // IE
        if (window.event != null) {
            if (key == 13) {
                document.getElementById(cPrefix.innerText + "ContentPane_btnLogin").click();
                evt.returnValue = false;
            }
        } else {
            // FF
            if (key == 13) {
                document.getElementById(cPrefix.innerText + "ContentPane_btnLogin").click();
                evt.preventDefault();
            }
        }
    } else {
        return;
    }
}