When I try to mark the url for copy-paste, I check/uncheck the checkbox instead.
I had the same problem too. The page has a problem because when I select something, it gets unselected. So there is no way to Copy the URL for example. What I did was, I selected the URL, then I press Ctrl + Print like if I am going to Print but then, I press ESC to cancel the Print. Once I do that, the URL is still selected then I can copy it by Ctrl + C for example and it works. I should not be like that, developers have to fix that because newbies learning how to code, are not going to be able to Copy and complete the task in order to move forward in the Course.