Neither would I, but it is valid HTML5 and it is demonstrated in the tutorial video.
As copying and pasting the code from the OP’s post into an HTML document produces the expected result for me, I can only guess that there is something else in the linked style sheet causing the issue - maybe something as simple as a missing curly brace, or a semi-colon instead of a colon.
@piano0011: if you are not already in the habit of using the W3Validators, I suggest you adopt it now. They will save you hours of frustration.
Nor would I. It was explained in the video as being “very helpful” when linking to another site and you don’t want the visitor to leave your site. It wasn’t explained that while the site owner may consider it helpful, for the visitor it is not - especially if they are relying on assistive technology. Personally, I choose to build sites for the convenience of visitors who use them, but judging by the prevalence of target="_blank" in code posted here, it seems many coders are unaware of the difficulties it poses. (More information: https://webaim.org/techniques/hypertext/hypertext_links#new_window.)
Agreed. Hopefully that will be covered in the next tutorial …