After installing Microsoft Office Web Apps (following the steps on http://technet.microsoft.com/en-us/library/ff431687(office.14).aspx#bkmk_ins_exis_sa) on a Microsoft SharePoint 2010 server, I got a HTTP Error 500.19 when accessing the SharePiont Sites.

Error

Config section ‘system.webServer/staticContent’ already defined. Sections must only appear once per config file. See the help topic <location> for exceptions

490:     </staticContent>
491:     <staticContent />
492:   </system.webServer

After removing the double <staticContent /> the site started working again.