Okay, sorry for that. Let's try getting rid of the preview window.
Zoom up the display to a high enough value to force the preview window off the screen. Again copy your code. Refresh and Reset. Paste your code back in. Make sure it is complete and doesn't have any infinite loop errors. When ready to run the code, zoom back out to 100%.
In the loop related lessons, use the following invalid code snippet to disable the auto-refresh.
<?php else ?>
Paste or type it in before starting the lesson. Remove when ready to test.