The problem here is you're using Flexible Squares, which is imported from LJ and not a DW supported layout, it's basically not as flexible as native DW stuff. To hide a specific element using CSS that element needs to have a name, the native DW layouts name each thing, but Flexible Squares doesn't.

I suspect the above layer code will have the same problem, it's for a Core2 layout, not an imported Core1 layout.

I would like it if someone with the coding skills made a CSS converter so people could swap Flexible Squares CSS over to a decent underlying layer instead, but it's completely beyond my ken.

So basically, Flexible Squares is less flexible than some other layouts...