diff --git a/web_viewer/index.html b/web_viewer/index.html
index 91a507df37e1..58dc70aa513b 100644
--- a/web_viewer/index.html
+++ b/web_viewer/index.html
@@ -44,15 +44,11 @@
 
       /* Position canvas in center-top: */
       canvas {
-        margin-right: auto;
-        margin-left: auto;
-        display: block;
         position: absolute;
-        top: 0%;
-        left: 50%;
-        transform: translate(-50%, 0%);
-        /* canvas must be on top when visible */
-        z-index: 1000;
+        top: 0;
+        left: 0;
+        width: 100%;
+        height: 100%;
       }
 
       /* Match the Rerun header bar. */