HTML页面禁用Enter键自动提交表单

<script language="javascript" type="text/javascript">
 //禁用Enter键表单自动提交
        document.onkeydown = function(event) {
            var target, code, tag;
            if (!event) {
                event = window.event; //针对ie浏览器
                target = event.srcElement;
                code = event.keyCode;
                if (code == 13) {
                    tag = target.tagName;
                    if (tag == "TEXTAREA") { return true; }
                    else { return false; }
                }
            }
            else {
                target = event.target; //针对遵循w3c标准的浏览器，如Firefox
                code = event.keyCode;
                if (code == 13) {
                    tag = target.tagName;
                    if (tag == "INPUT") { return false; }
                    else { return true; }
                }
            }
        };
</script>