I have Sitecore 8.1 as a multi site instance. The Experience Editor doesn't work, because the rendered URL seems to be rendered wrong. This is how Sitecore calls the Experience Editor:
https://hostname.com/de-DE/Site Name/Homepage/Startpage?sc_mode=edit&sc_resolvelanguage=1
If I remove the "de-DE/Site Name/Homepage/Startpage" part from the URL, it works.
EDIT: If I leave that part and add "sitecore/content/" at its beginning, it works too.
EDIT 2: Preview now works once I set preview.ResolveSite to true. Page Editor is still not working.
EDIT 3: Here's my SiteDefinition:
<site name="sitename" patch:after="site[@name='website']"
virtualFolder="/"
physicalFolder="/"
rootPath="/sitecore/content/Site Name/Homepage"
startItem="/Startpage"
hostName="*domain.com"
database="web"
language="de-DE"
domain="extranet"
allowDebug="true"
cacheHtml="true"
htmlCacheSize="10MB"
enablePreview="true"
enableWebEdit="true"
enableDebugger="true"
disableClientData="false"/>
Any idea what I can do to fix this?