(I will be using Fireworks in this tutorial, however, the same effect can be achieved in Photoshop.) Sorry about the screenshots. This board won't let me use a image url without a file extension such as .gif, .jpeg, etc.
Indented line:
First step:
Start a new file. Any canvas size is fine. Though, you must be the background as a shade of grey.
http://www.tinypic.com/5lyno9
Second step:
Using the line tool, make a line like the one showed below. Make sure its only 1 pixel wide and its the color black.
http://www.tinypic.com/5lyoap
Third Step:
Copy and then paste that line to make a duplicate. Drag the duplicate over to the right to the point where it is barely touching the original.(The x coordinate should only be 1 bigger than the original) Refer to the picture below.
http://www.tinypic.com/5lyq2u
Final Step:
Change the duplicated line to the color white. You now should have something that looks like this:
http://www.tinypic.com/5lyqdg
If you use different background colors you have to adjust the line colors so that it fits our background color. Other than that, its pretty simple and easy.

