Try a dummy static CSS file

Debugging LESS CSS compilation

media/css/persona.less

@@ -1,64 +1,5 @@
-@import "sandstone/variables.less";
-@import "sandstone/mixins.less";
-
-
-
-hgroup {
-    text-align: center;
-    padding-top: @baseLine * 2;
-    padding-bottom: @baseLine * 2;
-
-    h2 {
-        font-size: 48px;
-    }
-}
-
-#primary {
-    padding-top: @baseLine * 2;
-    padding-bottom: @baseLine * 2;
-    @shadow: 0 1px 1px rgba(0,0,0,0.1), 0 0 0 1px #fff;
-    .box-shadow(@shadow);
+body {
     background: #fff;
-    #gradient > .radial(center, 45px, ellipse, farthest-corner, #f5f1e8 0%, #ffffff 100%);
-    .clearfix;
-}
-
-#signin-example figcaption {
-    text-align: center;
-    font-style: italic;
-    color: @textColorSecondary;
-    margin: auto @gridGutterWidth  @baseLine * 2  @gridGutterWidth;
-}
-
-#openphoto {
-    text-align: center;
-    padding: @baseLine;
-    margin: @baseLine * 2  @gridColumnWidth + @gridGutterWidth;
-    border-top: 1px dotted @borderColor;
-    border-bottom: 1px dotted @borderColor;
-
-    p {
-        margin: 0;
-        .open-sans;
-        font-weight: 300;
-    }
-}
-
-#persona-themes {
-    text-align: center;
-    margin-top: @baseLine;
-    margin-bottom: @baseLine;
-    @shadow: 0 1px 1px rgba(0,0,0,0.1), 0 0 0 1px #fff;
-    .box-shadow(@shadow);
-    background: #fff;
-
-    h3 {
-        margin: 0;
-        padding: @baseLine;
-    }
-}
-
-#small-print {
-    text-align: center;
-    padding-bottom: @baseLine * 2;
+    color: #000;
+    font-size: 40px;
 }