1.one method:
(from the grid menu when editting a report).Then go Grid --> Options, slect the Columns and Rows tab and in the Fixed option select your attribute and set it to 0 pixels.
2.another method:
If you have OLAP Services, you can simply right click on the attribute and select Remove From Grid. Do NOT select Remove From Report as that will delete the attribute from the report SQL. Remove from Grid will allow you to hide the attribute without
having to remove it from the SQL used to create the results.