anchor.diff:            .block { color: #042 }
             ```
       .grid__row
  -      .grid__cell-xs_size_12.raw-text
  +      .grid__cell-xs_size_12.raw-text(style="border-left: 1px solid #ddd;")
           :markdown
             ## Element
             Elements are parts of a block and have no standalone meaning. Any element is semantically tied to its block.
       .grid__row
  -      .grid__cell-md_size_4.raw-text
  +      .grid__cell-md_size_4.raw-text(style="border-left: 1px solid #ddd;")
           :markdown
             #### Naming
             Element name may consist of Latin letters, digits, and dashes.
             CSS class is formed as block name plus two undercores plus element name:
             `.block__elem`
  -      .grid__cell-md_size_4.raw-text
  +      .grid__cell-md_size_4.raw-text(style="border-left: 1px solid #ddd;")
           :markdown
             #### HTML
             Any DOM node within a block can be an element. Within a given block, all elements are semantically equal.
  
positive.code:           ```html
            <div class="block_mod">...</div>
            ```
        .grid__cell-md_size_4.raw-text
          :markdown
            #### CSS
            Use modifier class name as selector:
  
negative.code:           ```html
            <div class="block">...</div>
            ```
        .grid__cell-md_size_4.raw-text(style="border-left: 1px solid #ddd;")
          :markdown
            #### CSS
             * Use class name selector only
  