My worst mistake (though it did help catch a bug which was cool) was not checking that my merge was done properly (we were using a terrible CM tool at the time and you had to merge manually). I had checked in some code that would, among other things, scale an image to a custom window space. I had missed one line of the code I had written to properly calculate the image bounds on window resize. As a result, whenever you would scale the window, the image dimensions would change erratically and screw up other behaviors based on image size. It shipped that way.