The View and Validate tabs are available only in Preview and Live site view modes.
On the View tab, you can see the actual appearance of the page in the selected mode. For more information on the differences between what can be seen on the tab in Preview and Live site mode, please see the Mode selection context help topic.
On the Validate tab, you can validate the page against the HTML and CSS standards and check if the page contains broken links.
Page url: http://devnet.kentico.com/docs/6_0/contexthelp/index.html?viewvalidate.htm