In the wake of the first federal government shutdown since 1996, the Department of Agriculture’s website has already been affected.
Visitors to the USDA website Tuesday and beyond will see this screen:

The Washington Post reported Monday that a number of government websites will be affected by the shutdown. The Federal Trade Commission and the Library of Congress sites will be taken offline, for example. And while some websites will not go down, many — including the Department of Veterans Affairs web page —will only be updated intermittently.