3 Pixel Border
This is the easiest way to create a 3 pixel border!
1. Open up your picture, we just used a black image, with a white background
2. Hit CTRL + A or get marquee tool to select all the image
Use marquee tool
3. Click Edit > Stroke - and give it these settings:
Stroke settings
4. Again click Edit > Stroke - but this time use the color white, and only use a stroke of 2px
5. Last time, click Edit > Stroke - settings are only 1px with #000000 (Black)
6. Thats it, hold CTRL and press D to deselect it
Final result
Even though it looks like the outside pixel is too thick, its really not, its just like there anyway, it will go when you save it
More Tutorials: 
