This is because of the sticky header menu.
What you will need is some way of offsetting it. Here is one example:
https://stackoverflow.com/a/13184714/24246072
Give...
Posted20 hours 57 min ago by Martin Price | System Horizons Ltd (yorkshirepudding) on:
Now only one problem left:
The link jumps to right under the H3 with the 'id' - why?
Do I need to set the id in something above where I want it - like a <div>?
The page...
Comments
I recommend the YouTube Field module. It has the option to be responsive and use the full width of whatever container it is in
There's also Video Filter if you are going to paste the videos into the body text.
I also use the "YouTube Field" module where there is a lot of content to embed.
If it's just a one-off... use iframes.