Just for information:
I’ve the layout object, only the “free licence” for the moment (in the js file : “v.2.0 build 81009”), and I saw a small problem in the dhtmlxlayout_dhx_blue.css.
It calls the image dhxlayout_bg.gif on line 43, but in the folder “\codebase\imgs\dhxlayout_dhx_blue” there is only a .PNG image.
Not a “serious” problem in fact, of course.
The issue was fixed in the latest layout version. But anyway thank you for the provided information.