404. That’s an error.
The requested URL /catalog/product_compare/add/product/846/uenc/aHR0cDovL3d3dy5lLWdyZWVudG91cmlzbS5jb20vY29hY2gtdGFza2VyLWJhZ2FnZS1sZWdhY3kuaHRtbA,,/form_key/ard091GmydZD1DWj/
was not found on this server. That’s all we know.