I just got a false positive the other day! They are very rare, though...they don't normally happen. They can be caused by three things: hCG shots at the doctor's office, faulty test, or you left the test sitting for too long. If you left it sitting for too long, it can cause an evaporation line...
I posted this in the NB & B section because all of you here are intelligent and give great answers. :)
I posted a similar question last night, but I wanted to ask in more detail. Last night, I took a pregnancy test and it came up with a very faint positive. The line was definitely there within...