diff --git a/controllers/class.ViewOnline.php b/controllers/class.ViewOnline.php
index 7d071db17..6b9ca3f0a 100644
--- a/controllers/class.ViewOnline.php
+++ b/controllers/class.ViewOnline.php
@@ -49,16 +49,19 @@ class SeedDMS_Controller_ViewOnline extends SeedDMS_Controller_Common {
 				 */
 				$this->params['content'] = $content;
 				if(null === $this->callHook('version')) {
-					header("Content-Type: " . $content->getMimeType());
-					$efilename = rawurlencode($content->getOriginalFileName());
-					if (!isset($settings->_viewOnlineFileTypes) || !is_array($settings->_viewOnlineFileTypes) || !in_array(strtolower($content->getFileType()), $settings->_viewOnlineFileTypes)) {
-						header("Content-Disposition: attachment; filename=\"" . $efilename . "\"; filename*=UTF-8''".$efilename);
-					} else {
-						header("Content-Disposition: filename=\"" . $efilename . "\"; filename*=UTF-8''".$efilename);
-					}
-					header("Cache-Control:  must-revalidate");
+					if(file_exists($dms->contentDir . $content->getPath())) {
+						header("Content-Type: " . $content->getMimeType());
+						$efilename = rawurlencode($content->getOriginalFileName());
+						if (!isset($settings->_viewOnlineFileTypes) || !is_array($settings->_viewOnlineFileTypes) || !in_array(strtolower($content->getFileType()), $settings->_viewOnlineFileTypes)) {
+							header("Content-Disposition: attachment; filename=\"" . $efilename . "\"; filename*=UTF-8''".$efilename);
+						} else {
+							header("Content-Disposition: filename=\"" . $efilename . "\"; filename*=UTF-8''".$efilename);
+						}
+						header("Cache-Control: must-revalidate");
+						header("ETag: ".$content->getChecksum());
 
-					sendFile($dms->contentDir.$content->getPath());
+						sendFile($dms->contentDir.$content->getPath());
+					}
 				}
 				break;
 		}