A. HTML and CSS-P-based content cannot overlap across frameset borders -- just as images can't. See the "Trees in Frames" section in the article at the following URL:
http://developer.iplanet.com/viewsource/smith_jstree/smith_jstree.html
A. HTML and CSS-P-based content cannot overlap across any native OS-based components, such as: framesets, applets, or even standard Form input elements. This is a web browser limitation that you'll need to work-around, e.g. by either re-arranging your content so that the trees don't overlap across the area, or by wrapping the native components inside an CSS-P element and then hiding that element when the tree is displayed.
A. To control the size of the tree items, set the following tree item width and height properties:
myTree.treeItemWidth = 200;
myTree.treeItemHeight = 20;