People make mistakes all the time. Just a couple days ago I made one here, and was promptly (and politely) corrected. The thing is though, seeing the mistake that was made can still help people, as long as it is marked as a mistake. Someone else may be doing the exact same thing, and not realize that what they are doing is potentially wrong.

If you look the node where I made my mistake (Re: Image display firefox problem) you'll see that it is clearly marked as being wrong, but people can still tell what I did wrong. You obviously put some effort into your original post, but now it has no chance of ever helping anyone.

In the future, I would consider leaving your answer in place and either correcting the mistake, or clearly marking it as wrong.