Oops, yes... thanks
sPECtre! I did forget to mention PS's vector tools!
If you're working strictly for web,
Plastic Guy, you can leave your resolution alone. It only comes into "effect" when producing for print purposes. Normal screen resolution is between 72 and 96 ppi and most web images are still produced at 72 ppi, for the benefit of the masses (those of us with monitors that still use this setting).
What I would suggest that you do is work at a much larger scale and then reduce down to the size that you intend to use. For example, take a look at this image. The rectangle on the left was created at "actual size"... the one on the right at 5x the size. Notice the difference in the "jaggies" when it was reduced down to match the size of the image on the left.
The other important thing is to use PS's vector tools whenever possible for drawing your shapes!