Using multiple sign-in with Google Sites
If you are signed in to multiple accounts through other Google products, going to http://sites.google.com will automatically sign you in to your default account (the first account you signed in to).
If at any time you close your browser window and then visit http://sites.google.com again, you will either be automatically signed in to the account from which you last accessed Sites, or you'll be prompted to sign in again to the account of your choice.
If you are having trouble with multiple sign-in on Sites, you may want to visit our known issues page.Google Apps users
If you are a Google Apps user, you may be looking on your 'My Sites' page for sites hosted either within your domain or outside your domain. When signing in to an additional account through multiple sign-in in Google Sites, the original page you were viewing prior to signing in to the additional account will be reloaded. If you feel that you are looking at the wrong "My Sites" list, it is possible that multiple sign-in has loaded a different "My Sites" page than what you were looking for.
As a Google Apps user, Sites will only load the sites list for one of the 'My Sites' lists—either the list for inside the Google Apps domain or outside the Google Apps domain. If you need to access a separate list of sites, look for the yellow box that says 'Looking for your sites…' to switch to sites inside or outside of the specified domain.
If you are having trouble with multiple sign-in on Sites, you may want to visit our known issues page.