code: function _includeCSSInternal (css) {
  		var head,
  			style = document.getElementById(_stylesheetTagID);
  
  		if (!style) {
  			// there's no our styles tag - create
  			style = document.createElement('style');
  			style.setAttribute('id', _stylesheetTagID);
  			style.setAttribute('type', 'text/css');
  			head = document.getElementsByTagName('head')[0];
  			head.appendChild(style);
  		}
  
  		if (style.styleSheet) {   // IE
  			style.styleSheet.cssText += css;
  		} else {                  // the others
  			style.appendChild(document.createTextNode(css));
  		}
  	}
docs: Add css code into STYLE tag in HEAD. It tries to use the single STYLE tag with special ID "xcss_styles"
  @param css - style