function checkEnter(e) { //e is event object passed from function invocation
    if (e.which || e.keyCode) {
        if ((e.which == 13) || (e.keyCode == 13)) {
            submitSearchForm();
            return false;
        }
    }
    else { return true };
}

function submitSearchForm() {
    if (document.getElementById("txtSearch").value == "") {
        alert("Please enter a keyword for your search.");
    }
    else {
        document.getElementById("q").value = document.getElementById("txtSearch").value;
        document.getElementById("qs").submit();
    }
}