I also use Dreamweaver and have several layers within, I think the reason your layers are appearing to be moving is because your page may be centering the content. And In the Design view you place the layer, (note in design view the main content of the page is not centered where it wll show in the browser) so actually the layer is exactly where it is suposed to be, the main page content moves to the center of the browser, thus making it seem that the layer has moved on you. So I found the only way to use layers accurately is to make a left and top margin, so that when you are in design view the placing of the layer is accurate. I may and I think I am wrong of your situation, you may already know this and I may be totaly wrong of you situation.
How to make margins if you dont know how, edit the body tag:
<body leftmargin="50" topmargin="10">
</body>
- Wildchild22 the z-index is the position of the layer "front to back" so If "layer 1" has a z-index of 1 and "layer 2" has a z-index of 2, "layer 2" will appear on top of "layer 1". If "layer 1" had a z-index of 3 then it would be above/on top of "layer 2".
The site 
