If you only see a partial view of your heads when casting a card, your browser settings might not be configured correctly.
Please maximize the browser screen, and zoom out of the page. Set zoom view to 100%.
Check that the text size on your screen is set to 'normal' or 100%.
You can also switch to 'full screen' option if you are using Internet Explorer. Hit F11 to get to 'full screen' mode.
If you are still having trouble, please check out this tutorial.