Hello all!

I've been trying to design a website for a couple of weeks now and it's been really stressful wanting to learn everything about html/5 and css/3 (I've just started learning), and I'm being pretty impatient.

What I've done is built a basic HTML5 structure with a navigation inside a header, you lose sight of the header/nav as you scroll down.

What I would like which I've failed at is an interface compatible with all browsers and devices, a design that adjusts to the users browser size not matter what browser/device. Which also allows zooming in on smaller devices like tablets/iPhones etc. Every aspect of the site needs to be fixed in place (at the moment my navigation moves up and down when I'm resizing the browser) where the user can move around and zoom in and out.

I've also read into the benefits of em, so I set the default font to 100%, and all the headers/paragraphs etc I set to em accordingly. Would it be wise to set all fonts to em and the rest of my website like margins etc to percentages?

Thanks for the help in advance!