diff --git a/sd/themes/simplex.min.css b/sd/themes/simplex.min.css
index acdfcef7cc223945d053339149961639f614f47f..a0bd9587b55d1992e151c8d275d6d0fc31e553e9 100644
--- a/sd/themes/simplex.min.css
+++ b/sd/themes/simplex.min.css
@@ -884,3 +884,5 @@ i[class^="icon-"]{opacity:0.5;vertical-align:-2px;}
 .invisible{visibility:hidden;}
 .affix{position:fixed;}
 a:not([href]){color:#555;}
+[data-caption] {position: relative;}
+[data-caption]::before{display:block;content:attr(data-caption);position:absolute;width:100%;background:rgba(255,255,255,0.5);color:gray;}