Remove flex, it's not well supported by safari

media/less/sign/sign.less

@@ -144,6 +144,7 @@ h2 {
     }
     div.AuthForm, div.updates {
         width: 100%;
+        float: initial;
     }
     div.updates {
         margin-top: 10px;
@@ -151,12 +152,4 @@ h2 {
     div.main_layer {
         padding: 0 20px;
     }
-    div.main_content {
-        display: -webkit-flex;
-        display: flex;
-        
-            -ms-flex-direction: column;
-        -webkit-flex-direction: column;
-                flex-direction: column;
-    }
 }