Blank page
https://www.zen-cart.com/tutorials/index.php?article=82
Then decided to play with a variation on the original page using the same editor, "Define_Page_3.php." Along the way, I tried to look atwww.mydomain.com/page_3.php or www.mydomain.com/define_page_3.php with no luck .
Those are not the url's to access load page_3
Once you get your blank page squared try
www.mydomain.com/index.php?main_page=page_3