How can I set a css border on one side only?

Question

For a given div I would like to only display a border on the left, right, top, or bottom side.

Currently I have the following, which puts a border on all sides:

#testdiv {    border: 1px solid; } 

What do I need to do in order to have a border only on the left side?

Answer 1

#testdiv {    border-left: 1px solid; } 

See the MDN documentation on border.

Answer 2

If you want to set 4 sides separately use:

border-width: 1px 2em 5px 0; /* top right bottom left */ border-style: solid dotted inset double; border-color: #f00 #0f0 #00f #ff0;