A majority of federal government agencies have their own websites, including major departments such as the State Department, the Department of Energy and the Department of the Treasury. State and local governments also often have Web presences. Government agencies at any level often have multiple additional sites devoted to specific functions or programs at separate addresses from their main websites.
Many major governmental agencies have websites separate from the website of their parent departments, such as the National Institutes of Health and the Internal Revenue Service sites that are distinct from the Department of Health and Human Services and the Department of the Treasury websites. These agencies often have unique websites devoted to specific functions, though these may be hosted as part of the main website's domain, as with the Public Health Image Library maintained by the Centers for Disease Control at phil.cdc.gov.
While the vast majority of U.S. government websites are hosted at domain names ending in ".gov," many military sites use domain names ending in ".mil," such as army.mil and marines.mil. State government websites typically use the ".gov" domain prefixed with the state's postal abbreviation, as in the ca.gov domain used by California state agencies. While counties, cities and other local government agencies can use ".gov" domains, some opt to use other top-level domain names, such as ".org," ".net" or ".com."