In IE 5.5+, layer will cover both drop-downs when WCH is applied. In IE 5.0x, only the first will be covered, as that is the one with WCHhider class.
This example shows the importance of passing a container. If your layer is nested in positioned element, then you must pass an id of or a reference to that element.
Otherwise, Hider will not be located where it's supposed to be (as shown by making the Hider visible, at the top of the page).
Note that wmode=transparent parameter is not used here.
This example (as well as previous one with Flash) uses the double-object technique.