Stupid, Illogical Computers

I'm so pissed that I can't figure out how to fix my blog! I spent a couple hours last night trying to fix it and it was fixed - temporarily. I showed it to DH - he can verify that it looked right. And then the next time I clicked on it, the sidebar info was again all at the bottom. WTF?!! I cannot figure out why it's doing that. I even went so far as to have my friend Karin make a test blog using the same template (working correctly) for me and compared the codes - exactly the same minus one line. I added that line but it didn't fix completely. Then I copied the test blog's code and pasted it on my blog (erasing what I had before). That should have made it look like the test blog, right?!!! WRONG!!! It makes no sense! This is supposed to be so logical, but it's driving me crazy because it's NOT!!