je ne comprends plus rien

assets/css/template.css

@@ -68,7 +68,7 @@ body {
 
 	.bg{
 		background-position: center center, center center;    
-		background-size: auto,100% 100%;
+		background-size: auto,100% 100vh;
 		background-attachment: fixed,fixed;
 		-webkit-background-attachment: fixed,fixed ;