fix bug

apps/exams/Tpl/default/Index/examsroom_w3g.html

@@ -343,10 +343,16 @@
 
     function stopBubbling(e) {
         e = window.event || e;
-        if (e.stopPropagation) {
-            e.stopPropagation();      //阻止事件 冒泡传播
-        } else {
-            e.cancelBubble = true;   //ie兼容
+        if(e.stopPropagation){
+            e.stopPropagation();
+        }else{
+            e.cancelBubble = true;
+        }
+
+        if(e.preventDefault){
+            e.preventDefault();
+        }else{
+            e.returnValue= false;
         }
     }