The RevitClinic has a great post on changing Revit 2012 to use either offline or online help.
Wax On / Wax Off: Changing Revit 2012 to use offline or online help
You may have noticed the new wiki help for Revit 2012. http:\\wikihelp.autodesk.com\revit
Just in case you don't have a internet connection, or simply want to use a local copy of help instead, a few changes to the Revit.ini can help.
Check out our previous post on the Revit.ini for more information about the 2012 ini file.
In the Revit 2012 ini there are two lines about help in the [Documentation] section:
[Documentation]
UseHelpServer=1
HelpBrowser=0
If UseHelpServer is set to 1 Revit will first look to the online wikihelp, if it cannot find a internet connection, it will pull up the local help instead. If you set UseHelpServer to 0 the local help will always be used.
If HelpBrowser is set to 0 Revit will use your systems default internet browser (whatever that may be). If you set it to 1, Revit will use Internet Explorer.
The wikihelp includes this information on the Online help page.
