Reply To: Nav bar causing scrolling

[bearhead]

Its because of this line:

* {
  border: 1px solid black;
}

You’re applying a 1px border to every element on the page. All those borders are adding up to push the width of the page beyond 100% of the screen size.

You should remove that line and apply your borders more judiciously. For elements that have borders, you may also want to consider using:
box-sizing: border-box;

Additionally, you should add the following lines:

body{
  margin:0;
}
#nav ul{
  padding:0;
}

You can remove the margin:-10px; on #nav