Index: typo3/sysext/viewpage/view/index.php
===================================================================
--- typo3/sysext/viewpage/view/index.php	(revision 6908)
+++ typo3/sysext/viewpage/view/index.php	(working copy)
@@ -109,6 +109,12 @@
 			$addCmd = '&ADMCMD_view=1&ADMCMD_editIcons=1'.t3lib_BEfunc::ADMCMD_previewCmds($this->pageinfo);
 		}
 
+			// preview of mount pages
+		if ($this->pageinfo['doktype'] == 7 && $this->pageinfo['mount_pid_ol'] > 0 && $this->pageinfo['mount_pid'] > 0) {
+			$addCmd .= '&MP=' . $this->pageinfo['mount_pid'] . '-' . $this->id;
+			$this->id = $this->pageinfo['mount_pid'];
+		}
+
 		$parts = parse_url(t3lib_div::getIndpEnv('TYPO3_SITE_URL'));
 		$dName = t3lib_BEfunc::getDomainStartPage($parts['host'],$parts['path']) ?
 						t3lib_BEfunc::firstDomainRecord(t3lib_BEfunc::BEgetRootLine($this->id)):