docs: function(parser, reporter){
          var rule = this;
  
          //count how many times "float" is used
          parser.addListener("property", function(event){
              var parts = event.value.parts,
                  i = 0, 
                  len = parts.length;
  
              while(i < len){
                  if ((parts[i].units || parts[i].type == "percentage") && parts[i].value === 0){
                      reporter.warn("Values of 0 shouldn't have units specified.", parts[i].line, parts[i].col, rule);
                  }
                  i++;
              }
  
          });
  
      }