Sql Reporting Services has an issue with firefox in which reports will show about one inch tall in the report viewer. There is an easy fix for this, but it seems to depend on the version of firefox.
It seems to be the support of attributes on IFrame in firefox.
I'm running on 3.05 and the following works for me:
C:\Program Files\Microsoft SQL Server\MSSQL.3\Reporting Services\ReportServer\Pages\reportviewer.aspx
make sure this is in the body tag (prob is by default):
<body style="margin: 0px; overflow: auto">
and the report viewer line should have this added to it: style="display:table;"
<RS:ReportViewerHost style="display:table;" ID="ReportViewerControl" runat="server" />
Some say add one of the following to the ReportingServices.css, however that did not work for me. The above fix did however.