Generated by SassMeister.com.

SassMeister-input-HTML.html

<div id="homepage">
  <div class="homepage-navbar">
    
  </div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.3)
// Compass (v1.0.1)
// ----

/* Navbar styles common to all pages */
%navbar {
 height: 100px;
 background: blue;
}

/* Navbar styles specific to homepage */
#homepage {
  background: yellow;
  height:1000px;
}

.homepage-navbar {
  @extend %navbar;
  background: green;
}

SassMeister-output.css

/* Navbar styles common to all pages */
.homepage-navbar {
  height: 100px;
  background: blue;
}

/* Navbar styles specific to homepage */
#homepage {
  background: yellow;
  height: 1000px;
}

.homepage-navbar {
  background: green;
}

SassMeister-rendered.html

<div id="homepage">
  <div class="homepage-navbar">
    
  </div>
</div>