On some systems with enhanced browser security settings (such as Internet Explorer 8 on Windows Server 2008), the Expand and Collapse icons (+ and -) in the Table of Contents might fail to work. To fix the issue, enable JavaScript in your browser:
Internet Explorer: Click Tools > Internet Options > Security tab > Internet zone > Custom level, then select the Enable option for the Active Scripting feature.
Firefox: Click Tools > Options > Content tab, then select the Enable JavaScript option.