404. That’s an error.
The requested URL /catalog/product_compare/add/product/686/uenc/aHR0cDovL3d3dy5sb2phbnV0cml2aWRhLmNvbS9mYW50b2NoZS0zLmh0bWw,/ was not found on this server. That’s all we know.
/catalog/product_compare/add/product/686/uenc/aHR0cDovL3d3dy5sb2phbnV0cml2aWRhLmNvbS9mYW50b2NoZS0zLmh0bWw,/