Update yu.html

Author: vectorZeng

more/content/yu.html

@@ -34,7 +34,10 @@
 }
 
 .happy-valentines {
-  position: relative;
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
   width: 550px;
   height: 600px;
   display: flex;