Suppose you’re displaying a report in a or an from a report server through a URL. If the report has a drill down report, the new report will come out of the frame and cover the entire browser screen. This is because the target defaults to _Top, which opens the report out of frame.
To have control over the report display, SSRS comes with a report parameter: rc:TargetLink. Using this parameter, you can force the report to open in the required frame. For example:
It’s a good practice to provide the frame name as the target link, because this complies with both 2000 and 2005 versions: