anchor.diff:  
             If you think that in your case you would have a global modifier, these are the problems you may face:
   
  -          First of all the specifity problem appears. In a local modifier case CSS code goes like this:
  +          First of all the specificity problem appears. In a local modifier case CSS code goes like this:
   
             ```css
             .block {
  
positive.code: 
          ul
            li
              a(href="#why-the-modifier-classes-are-prefixed") Why the modifier CSS classes are prefixed with their parent block name?
            li
              a(href="#can-i-create-global-modifier") Can I create a modifier global applicable to any block? Like visible/invisible.
  
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          a(id="why-the-modifier-classes-are-prefixed")
          :markdown
            ## Why the modifier CSS classes are prefixed with their parent block name?
  
            > BEM recommends to modify blocks like this `<div class="block block_mod">`. Why not to use the simple version like `<div class="block mod">`? Since we now have combined selectors `.block.mod`, it's easy to define all the CSS properties to it.
  
            The recommendation to prefix modifier CSS class with its block name has multiple reasons.
  
            Firsly, since it is possible to mix several blocks an elements at the same DOM node, we need to ensure that a modifier would affect only
            the block it belongs to. Let's say that we have a menu item element and a button mixed together. In HTML this construction is represented
            by the following markup:
  
  
negative.code:           notation, it is pretty natural to write `&_mod` there and finally get a modifier declared as it was recommended.
          a(id="can-i-create-global-modifier")
          :markdown
            ## Can I create a global modifier applicable to any block? Like `visible`/`invisible`.
  
            > I've heard that global modifiers like `visible`, `invisible`, `red`, `opacity50` are not welcomed in BEM. Why?
            > I think it is useful to incorporate common properties like this in such a global class and then apply it to different blocks.
  
            Indeed you can have 2 main CSS classes at the same DOM node. In BEM we call it `mix`:
  
  