Based on your last post You are using external stylesheets (plural) - is this accurate? (The following assumes this situation.)
As no one else has responded yet - and your question is not in my realm of Hype experience (external style sheets - so far used only internal styles)... but I have one idea (maybe two).
One thing to examine: Is the "Protect from external styles" checkbox in the Documents Inspector deselected? If it is checked it may be interfering with your external styles.
The thing I don't understand is why your embedded Hype document "always want to be at the top of the page". Assuming You are placing it in a
<div> (or something similar) lower down on the page - how is it getting out of the corral? Do You have an absolute position setting affecting things?
Would You consider putting your style sheet in the
<head> of your Hype document?
If You are still getting no where would make your Hype project available for examination?
Also, please read this:
The post You might find useful is #7 from Stephen (last one currently)... though the whole thread might prove illuminating.