I'm new to web development, the syntax mianly. I added an external style sheet to test things out. I'm added a div id to that style sheet that has some random nonsense to see how it works but it's not working in my index.html. The style sheet IS working properly because it changes the body background color, but not the div stuff. What am I doing wrong here?
<link rel="stylesheet" href="mainStyle.css">
border:2px solid red;