Issue:
an error occurred during local report processing.the definition of the report'Main Report'is invalid.
The report definition is not valid.Details:Data at the root level is invalid.Line 1,position 1.
Answer:
1.please check these items,while publish the website:
Allow this precompiled site to be updatable.
Use fixed naming and single page assemblies when you publish web site.
2.set up the ReportViewer.exe(Microsoft Report Viewer Redistributable 2008 Setup) on the site server.