diff --git a/doc-src/content/stylesheets/main.sass b/doc-src/content/stylesheets/main.sass
index f8e50822..adbea73a 100644
--- a/doc-src/content/stylesheets/main.sass
+++ b/doc-src/content/stylesheets/main.sass
@@ -68,6 +68,12 @@ body.reference
       a.permalink
         +hover-link
         +link-colors("inherit", "inherit")
+    .arg[data-default-value]
+      color: #666
+      &:before
+        content: "["
+      &:after
+        content: "]"
   .source-documentation
     background-color: #eee
     border: 1px solid #aaa
diff --git a/doc-src/layouts/default.haml b/doc-src/layouts/default.haml
index a60a4999..6732ad74 100644
--- a/doc-src/layouts/default.haml
+++ b/doc-src/layouts/default.haml
@@ -25,5 +25,9 @@
          e = $(e);
          e.after('<span class="swatch" style="background-color:'+e.text()+';"></span>');
         });
+        $('span.arg[data-default-value]').each(function(i,e){
+          e = $(e);
+          e.attr("title", "Defaults to: " + e.attr("data-default-value"))
+        })
       });
     = render "partials/analytics"
diff --git a/doc-src/lib/stylesheets.rb b/doc-src/lib/stylesheets.rb
index 7455e0b0..884e47e5 100644
--- a/doc-src/lib/stylesheets.rb
+++ b/doc-src/lib/stylesheets.rb
@@ -135,8 +135,8 @@ def constants(item)
   constants
 end
 
-def mixin_signature(mixin)
-  mixin.sass_signature(:include)
+def mixin_signature(mixin, format = :html)
+  mixin.sass_signature(:include, format)
 end
 
 def example_items
diff --git a/doc-src/lib/stylesheets/sass_extensions.rb b/doc-src/lib/stylesheets/sass_extensions.rb
index db998da0..6881fd77 100644
--- a/doc-src/lib/stylesheets/sass_extensions.rb
+++ b/doc-src/lib/stylesheets/sass_extensions.rb
@@ -118,30 +118,36 @@ module Sass
         "#{sass_signature}\n  #{children_to_sass}\n"
       end
 
-      def sass_signature(mode = :definition)
+      def sass_signature(mode = :definition, format = :text)
         prefix = case mode
         when :definition
           "="
         when :include
           "+"
         end
-        "#{prefix}#{name}#{arglist_to_sass}"
+        "#{prefix}#{name}#{arglist_to_sass(format)}"
       end
 
       private
-      def arglist_to_sass
+      def arglist_to_sass(format = :text)
         if args && args.any?
-          "(#{args.map{|a| arg_to_sass(a)}.join(", ")})"
+          "(#{args.map{|a| arg_to_sass(a, format)}.join(", ")})"
         else
           ""
         end
       end
-      def arg_to_sass(arg)
+      def arg_to_sass(arg, format = :text)
         name, default_value = arg
-        sass_str = "#{name.inspect}"
-        if default_value
-          sass_str << " = "
-          sass_str << default_value.to_sass
+        sass_str = ""
+        if format == :html
+          ddv = %Q{ data-default-value="#{h(default_value.to_sass)}"} if default_value
+          sass_str = %Q{<span class="arg"#{ddv}>#{name.inspect}</span>}
+        else
+          sass_str = "#{name.inspect}"
+          if default_value
+            sass_str << " = "
+            sass_str << default_value.to_sass
+          end
         end
         sass_str
       end