阻止事件执行默认行为

    <img alt="" src="Images/Anchoring.PNG" width="120px" height="120px"/> 
    <script type="text/javascript">
        function blockEvents(evt) {
            evt = (evt) ? evt : window.event;
            var elem = (evt.target) ? evt.target : ((evt.srcElement) ? evt.srcElement : null);
            if (elem&&elem.tagName&&elem.tagName.toLowerCase()=="img") {
                if (evt.cancelBubble) {
                    evt.cancelBubble = true;
                }
                alert("Sorry,feature not available!");
                return false;
            }
        }
        document.oncontextmenu = blockEvents;//阻止右键点击图片
    </script> 
    <a href="" onclick="return submitForm();">submit</a>
    <script type="text/javascript">
        function submitForm() {
            document.forms["form1"].submit();
            submitForm = blockIt;//阻止重复点击提交
            alert(0); return false;
        }

        function blockIt() {
            return false;
        }
    </script>