In visual studio, the report and all his subreports are rendering well, but in the browser I have the following error message on every subreport : Format of the initialization string does not conform to specification starting at index 0. The parameter is a string (the id of an employee) and subreports show other data from that employee. My project is a web app (ASPx) on sql server 2008 and VS 2010. Thanks for help (I am a french speaker, so...)