fixes non-retina shadow and browser zoom issue

app/assets/stylesheets/pages/notes.scss

@@ -75,6 +75,8 @@ ul.notes {
         display: none;
         padding: 10px 0 0;
         cursor: pointer;
+        position: relative;
+        z-index: 2;
 
         &:hover {
           color: $gl-link-color;
@@ -118,11 +120,11 @@ ul.notes {
           &::after {
             content: '';
             width: 100%;
-            height: 20px;
+            height: 67px;
             position: absolute;
             left: 0;
-            bottom: 50px;
-            background: linear-gradient(rgba($gray-light, .3) 0, $white-light);
+            bottom: 0;
+            background: linear-gradient(rgba($gray-light, 0.1) -100px, $white-light 100%);
           }
 
           &.hide-shade {