Community Server on Windows 2008
When you've installed Community Server on Windows 2008 and especially are running under IIS7, you'll probably get some problems with at least your tags. Community Server will throw a 404 "Page not found" error on tags with spaces. If that's the case, open up your web.config and paste the following code at the bottom, but within the "configuration" tags.
<requestFiltering allowDoubleEscaping="true" />
Now IIS7 might still throw an error because the configuration won't allow you to overrule the default setting. In this knowledge base article you'll find more information.
Find the following file %windir%\System32\inetsrv\config\applicationHost.config and open it in Notepad under Administrator permissions. Find the key 'requestFiltering' and set overrideModeDefault to "Allow" instead of "Deny".
When your avatars aren't showing, it might be because you're running in "Classic .NET AppPool" mode and not in "Integrated Pipeline". Change it and it should work.