Graphs may not be rendered correctly if some browser settings are disabled.
Make sure Java Plug-in is enabled:
1. Go to Tools > Manage Add-Ons
2. Find the Java Plug-in
3. Make sure it is enabled
Make sure that the browser has Show pictures turned "On":
1. Go to Tools > Internet Options
2. Go to Advanced tab
3. Enable Show pictures
4. Click Okay
Note: The steps above applies to Internet Explorer. Steps vary for other browsers.