There is probably a mistake or syntax error. I would use Google to find some examples of how such a rewrite rule should look like. Or, although it is not clear what you want to achieve, but if you are using portal engine, you can use this setting in Kentico: Settings -> URLs and SEO -> Process domain prefix So, with this setting you can e.g. enforce always to have www or non-www URL or leave it as it is. But in general, handling this on the IIS level using the rules is better for performance.