"Off Site" lets you download static webpages from a webserver for offline viewing. To be able to use this app, the webserver has to supply a manifest file according to the "cache.manifest" standard. This manifest file lists all pages and other files (like images) that are to be downloaded for offline viewing.
PLEASE NOTE: A normal webserver does NOT do this per default. This has to be explicitly enabled by a webmaster - most likely your intranet web administrator.
If you are not sure if this app will work with the webserver that you want to view offline, please check with the webmaster of that webserver.