The following sample code shows how you can start a website:
[C#]
using CMS.SiteProvider; 
 ... 
 // Get site object by code name SiteInfo si = SiteInfoProvider.GetSiteInfo("CorporateSiteASPX"); 
 // If site exists if (si != null) { // Run site SiteInfoProvider.RunSite(si.SiteName); }  | 
The following sample code shows how you can stop a website:
[C#]
using CMS.SiteProvider; 
 ... 
 // Get site object by code name SiteInfo si = SiteInfoProvider.GetSiteInfo("CorporateSiteASPX"); 
 // If site exists if (si != null) { // Stop site SiteInfoProvider.StopSite(si.SiteName); }  | 
Page url: http://devnet.kentico.com/docs/5_5r2/devguide/index.html?starting_and_stopping_websites.htm