gistfile1.txt

@import compass/utilities/general/inline_block.sass
.my-nav
  .tabs
    li
      :border none
      .tab_l, .tab_t, .tab_r
        +inline-block
        :background-repeat no-repeat
        :height 35px
        :color red
      .tab_l, .tab_r
        :color transparent
      .tab_l
        :background-position top left
        :background-image url('/images/redesign/my/default-button-left-corner.gif')
      .tab_t
        :background-position top center
        :background-image url('/images/redesign/my/green-default-button-stretch.gif')
        :background-repeat repeat-x
        :text-align center
        a
          :margin-top 7px
      .tab_r
        :background-position top right
        :background-image url('/images/redesign/my/default-button-right-corner.gif')

gistfile2.txt

%li{:class => "#{my_tab.css.join ' ' unless my_tab.css.empty?}"}
  %span.tab_l
      
  %span.tab_t= link_to my_tab.title, my_tab.url
  %span.tab_r