修改tab样式

@@ -71,13 +71,15 @@
     .channel-tab {
         position: fixed;
         top: 0;
-        left: 0;
+        left: 50%;
         z-index: 1;
         width: 100%;
+        max-width: 750px;
         height: 90px;
         font-size: 24px;
         text-align: center;
         background: #fff;
+        transform: translate(-50%, 0);
 
         .channel {
             display: inline-block;