Auto-collapse children records

Children records at the top of a Master-View page look like collapsible sections. I want them to be collapsed initially, so I need to put some JavaScript code at the Master page's onLoad section, something like the code that's here http://xlinesoft.com/phprunner/docs/how_to_work_with_foldable_section.htm
Anyone done this before? Do you know the jQuery selector that I have to use to select these sections?
Thank you in advance
jimb