I’ve noticed a spike in 404s on several of my sites for browserconfig.xml. Turns out Windows 8.1 looks for this file automatically when a site is pinned to the start screen.
This file allows you to define several things, including graphics to use for various size tiles and also an RSS URL so you can update your readers when you have new content. Pretty neat. I doubt other browsers or OSs will pick up on it, but if you are noticing 404s for it in your logs, it may be worth the effort to throw a browserconfig.xml file together.
Microsoft conveniently provides a tool for doing this. It allows you to do the basics and will even resize your images for you. They also provide in-depth documentation on the file format in case you want to get more advanced.
I’m in the process of rolling this out to my sites, so no idea yet on whether the notifications will actually drive traffic, but it is so easy to set up that it is worth the initial effort.