I've observed that searching for multi-word tags is broken, e.g. http://www.ormfoundation.org/tags/Bug+Report/default.aspx
This is an issue that affects Community Server when running on IIS7.x and can be easily fixed by adding the following to the <system.webServer> section in web.config:
<requestFiltering allowDoubleEscaping="true" />
Thanks for your suggestion.However, the "double escape" functionality is disabled as a website design feature.