Don't separate content artificially

Don't display different content based on IP, browser type or version, operating system or whatever. This is very tempting for most Web designers, as it's a way to show you know how to write JavaScript or another programming language. But it can look like you're trying to trick the search engine - showing it something other than you show your readers. If you really must display alternate content based on some artificial measure, create separate Web pages for each, rather than using the same URL for all the content. Or, keep the content that is different as minimal as possible, don't build an entire new site for each IP or browser type.