diff --git a/css/knacss.css b/css/knacss.css
index 9a77b74..54c921d 100644
--- a/css/knacss.css
+++ b/css/knacss.css
@@ -138,6 +138,18 @@ mark {
 	padding:2px 4px;
 	background: #ff0;
 }
+/* avoid bad line-height */
+sup,
+sub {
+  vertical-align: 0;
+  position: relative;
+}
+sup {
+  bottom: 1ex;
+}
+sub {
+  top: .5ex;
+}
 
 table { margin-bottom: 1.5em; }
 
@@ -534,4 +546,4 @@ textarea {
 	body {
 		-webkit-text-size-adjust: 100%;
 	}
-}
\ No newline at end of file
+}