How Get $Site.CurrentSiteUrl in formula editor

If we want to see the current site url in HYPERLINK function of formula editor, this is how it should be done. 

LEFT($Api.Partner_Server_URL_260, FIND( '/services', $Api.Partner_Server_URL_260))

Reference: http://salesforce.stackexchange.com/questions/3816/how-do-i-get-the-base-url-in-the-formula-editor