Hi there,
There are some helpers on static pages that attempt to make it a bit like a
WYSIWYG editor, so for example it will interpret carriage returns as line breaks, etc. This can break HTML, so what I have found works in the past is to remove all line breaks and indentation from your HTML in blocks when it's ready to go into the page.
If you log in using the credentials on the homepage, you can enter edit mode and look at
this Help page on the AtoM demo site as an example - there's a small table there for example. To get it to work, I had to remove all the linebreaks and indentation that normally makes HTML more human-readable - but this allowed it to bypass the formatting helpers that were preventing the HTML from working as expected.
Hopefully experimenting with this a bit will help you - good luck!