I just published my first game to the site as part of a game jam. I set it up as a HTML game, to run in the browser. It is running but its getting the screen cut off on all sides. I'm not sure what's causing this. I used to Unity to make the game. When I run the file on my computer the browser can play the game fine. It's not cutting the size down or anything. Once it's loading through the itch.io page, not only is it cutting off the sides of the game but, it's not even showing the little Unity banner at the bottom with the fullscreen option. 

I've seen other Unity web player games run just fine on this site. I'm just trying to find out what I'm doing wrong

Hello, you have to set the size of the game's viewport a little larger in order to fit the entire game. You can find the size options on your project's edit page. Thanks

Thank you, I completely missed that section. Fixed my issue instantly!