Help with Problem

I'm trying to put a different cursor on my Big Cartel site but have never done anything with CSS. I've been copying the CSS coding from various cursor websites and pasting it into the CSS on my Big Cartel site but none of them are working. Here are some examples of the codes that I'm putting in:

Hey guys, I wanna ask you how to make some div with hover with one will change sizes and after that some text will show up becouse
text is too big for div in basic size.
Thanks for some help.

Hi. I'm going a bit loopy. Probably beeen looking at code too long but just cant see what the problem is. My drop down menue for mobile users/small screens displays and nearly works, its just the links in it dont seem to register.
I tried relative and full urls and other tests but ive drawn a bit of a blank
its the bit im concerned with

<div id="header">
  <div class="container"> 
    <!-- Header | Logo, Menu
		================================================== -->

Hi
I'm working on a gallery/shop of artwork. I did a test page, just lightbox code i found. but when I put it in my actual web page it opens the image but none of the next, back, close links.
Anyone know if theres an obvious reason why this would not work.
i'm guessing its some sort of code clash but im not too hot with this stuff

Thanks

I am a first year student in comp sci so I have the very basics of html and css down, but someone has asked me to make a site for them so I tried. The problem I am having with the layout which goes absolutely haywire when I zoom in/out or inspect the site on the mobile devices in chrome. And also I find that white space in the site looks off and I am not sure what to do there.