change how offscreen css is defined. finxes #1011

select2.css

@@ -589,8 +589,14 @@ disabled look for disabled choices in the results dropdown
 }
 
 .select2-offscreen {
+    border: 0;
+    clip: rect(0 0 0 0);
+    height: 1px;
+    margin: -1px;
+    overflow: hidden;
+    padding: 0;
     position: absolute;
-    left: -10000px;
+    width: 1px;
 }
 
 /* Retina-ize icons */