Top Menu child items behind modules in Host

Top menu child items drop behind the right column modules (and behind the content pad if no modules are published). In layout.css and template.css.css, I've added z-index:99999; to every bit of css code that has nav, menu or topmenu with no results.

This has nothing to do with the Seminar component or the Search module, as it still happens with plain article drop down children and no modules showing.

Please look at Seminar menu item children in top menu at: www.wk52.com

Thank you.

add this to layout.css:

#topmenu{
position: relative;
z-index: 999999;
}

I guess I tried every variant except the right one.
Thank you.