Question: When did the web accelerator 'CACHEbox' and browser 'Internet Explorer' become compatible?
SQL: 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'