I have had this too.. I think we just want to conceive so badly, we hope for any little indication.. so when its anything but stark white, it gets our hopes up! It's horrible to go through, I do it myself.
I know a lot of you guys have probably seen the site peeonastick.com, it's where I got this info:
"Most often the error lies in the interpretation. It's easy to squint, tilt the test, scan it and invert the color with a photo program, or try any number of tricks to see a positive result. (I've done it-- I know that of which I speak!) All tests are prone to evaporation lines-- a gray, colorless, "ghostlike" line, or a "dent" in the test in the place where a positive line would be.
All tests have two antibody strips in the test window. One of these lines will always turn pink (the control line) when exposed to moisture. The other line will turn pink only if exposed to moisture with hCG (pregnancy hormone.) These antibody strips are not invisible. They are difficult to see, but they're there. When exposed to moisture, the "results" line becomes easier to see (because the moisture causes the light to reflect differently.) When you scrutinize the test, therefore, you will always see "something" there. Alas, it doesn't count unless it is obviously pink (or blue, obviously, if using a test with blue dye.) If you can't tell what color it is or it's too faint, assume it is negative."