If it looks like the image below then either WebGL has crashed or they have disabled it.

Solution 1 :

You can empty cache & hard reload the browser, It can also remove the errors.

To Empty Cache & Hard Reload the browser, Please follow steps from below link. Below steps are specifically for Chrome Browser.

1.Open Developers tool by following path – Open View → More Tools → Developers Tools in Chrome or using below shortcuts.

In Mac – ⌥ + ⌘ + I
Windows – F12

2. Right mouse click on “Reload this page” button.

3. Select “Empty Cache and Hard Reload”.

4. Close Developer Tools.

5. Your Browser Cache is empty now and browser is hard reloaded.

Solution 2 :

Please alert them to this, and point them towards this guide to ensure it is enabled properly:

http://superuser.com/questions/836832/how-can-i-enable-webgl-in-my-browser