Issue with links and css updates

Link: http://thecornellproject.epizy.com/Project%20Homepage/

This website (the homepage only) consists of two main parts, the nav bar and the main content (the table and “your map” heading). The nav bar is supposed to link to other pages when each button is clicked and the logo in the corner is supposed to link back to the homepage in typical nav bar style. However, even though the code is written for each of these buttons to navigate to a different page, they seem to be acting as static pieces of text. Furthermore, they were working only a couple of days ago and I’ve made no direct changes to them since then. I can upload the code to allow for checking but I don’t think it’s problem as I use the same code in the table and it works fine. Also whenever I make an update to my css file, no matter what device I’m on, simply refreshing the page isn’t enough to display the updates. Instead I have to clear all of my browsing data as if the CSS file was somehow saved to my browser which hinders the editing process. 

Any suggestions to help get things working again? I’ve got a rather large grade riding on this.

-A

To display updates use Ctrl+F5, also clean the cache, you can load any page from the null if you need it at Google Chrome(other browser has pure functional to clear cache as I know) via Empty Cache and Hard Reload option, google it.
About your code errors — I’d like to help but you’d get much better help at such resources as stackoverflow

I checked the page, and the issue appears to be a code issue, not a caching issue.

In the source code, I see the completely valid tags with links. But the buttons aren't clickable for me either.

But when I double click the button, the "Your Map" text is highlighted. So there is some kind of transparent HTML element on top of it.

I suspect this is caused because the main-content section is using padding, not margin, to sit below the menu bar. It's probably a good idea to learn the difference between the two: https://www.w3schools.com/css/css_boxmodel.asp