SELECT T1.compatible_since_year FROM accelerator_compatible_browser AS T1 JOIN browser AS T2 ON T1.browser_id  =  T2.id JOIN web_client_accelerator AS T3 ON T1.accelerator_id  =  T3.id WHERE T3.name  =  'CACHEbox' AND T2.name  =  'Internet Explorer'
When did the web accelerator 'CACHEbox' and browser 'Internet Explorer' become compatible?
[Schema (values) (types)]: | browser_web |  Web_client_accelerator : id (text) , name (number) , operating_system (text) , client (text) , connection (text) | browser : id (text) , name (number) , market_share (text) | accelerator_compatible_browser : accelerator_id (text) , browser_id (number) , compatible_since_year (text);