I took a pregnancy test yesterday afternoon and it immeditaly came out positive. And was still positive later that day.However I looked at it today and it says negative. What does this mean?

That means that you are pregnant.

Reading the test is only accurate within the first few minutes after taking it. Most directions say 5 or 10 minutes after taking the test. Waiting longer than that is giving you a false reading.

Once you take a test and get the result, throw it away.

Yes, you let it lay around all day ?

But yes it means it is positive. If you want a second check, do another check the next morning.