code: function (sel,css) {
              var rule = cssRules[sel],
                  multi = sel.split(/\s*,\s*/),
                  remove = !css,
                  rules, i;
  
              // IE's addRule doesn't support multiple comma delimited selectors
              // so rules are mapped internally by atomic selectors
              if (multi.length > 1) {
                  for (i = multi.length - 1; i >= 0; --i) {
                      this.unset(multi[i], css);
                  }
                  return this;
              }
  
              if (rule) {
                  if (!remove) {
                      if (!lang.isArray(css)) {
                          css = [css];
                      }
  
                      workerStyle.cssText = rule.style.cssText;
                      for (i = css.length - 1; i >= 0; --i) {
                          _unsetProperty(workerStyle,css[i]);
                      }
  
                      if (workerStyle.cssText) {
                          rule.style.cssText = workerStyle.cssText;
                      } else {
                          remove = true;
                      }
                  }
                  
                  if (remove) { // remove the rule altogether
                      rules = sheet[_rules];
                      for (i = rules.length - 1; i >= 0; --i) {
                          if (rules[i] === rule) {
                              delete cssRules[sel];
                              _deleteRule(i);
                              break;
                          }
                      }
                  }
              }
              return this;
          }
docs: <p>Unset style properties for a provided selector string, removing
  their effect from the style cascade.</p>
  
  <p>If the selector includes commas, it will be split into individual
  selectors and applied accordingly.  If there are no properties
  remaining in the rule after unsetting, the rule is removed.</p>
  
  <p>The style property or properties in the second parameter must be the
  <p>JavaScript style property names. E.g. fontSize rather than font-size.</p>
  
  <p>The float style property will be unset by any of &quot;float&quot;,
  &quot;styleFloat&quot;, or &quot;cssFloat&quot;.</p>
  
  @method unset
  @param sel {String} the selector string to apply the changes to
  @param css {String|Array} style property name or Array of names
  @return {StyleSheet} the StyleSheet instance
  @chainable