If you are referring to this question, it was migrated because it does not meet the requirements for Super User, as described in the FAQ. It is related to a website, albeit the SE network itself.
Furthermore, I don't really consider that a question, since you answered it yourself, and it was more a tip, since you don't need to create the search yourself in Chrome as it is automatically added to the search list the first time you visit the site with Chrome, as are all the other sites in the SE network. Why not just create a blog post about?
It was either going to be migrated to Web Apps, or it could as a long shot belongs on MSO if anywhere on the SE network, however it would most likely have been closed on the latter.
an unrelated and not really popular stack exchange partner site
Actually, Web Apps is a just launched official Stack Exchange site, and it's purpose is to take exactly the type of questions you asked. It's the first site to ever leave Beta and should by no means be underestimated.
Before posting questions on Super User please read the FAQ. Once done spend some time learning how the site works. The first and most important thing to understand is Super User is not a forum. It is a Q&A site and has a very strict closing and moderation policy, which encourages high quality questions and answers.