html {
       background-image: url('http://hdwallpapersfactory.com/wallpaper/abstract_cubes_rubiks_cube_desktop_5120x4096_hd-wallpaper-1048163.jpg');
       color: green;
   }
    .gallery {
      width: 700px;
      
    }
    .gallery img {
      height: 100px;
      border-width: 5px;
      border-color: #ffffff; 
      border-style: solid;
      box-shadow:;
    }
    .main-menu a {
    background-color: #00FF00;
    border-color: #00DD00;
    font-weight: bold;
    display: inline-block;
    padding: 5px 10px;
}

.main-menu a:hover {
    background-color: #00DD00;
    color: #FFFFFF;
}