You are referring to the old instructions. Refer the updated instructions in wiki <http://wiki.maemo.org/Mer/Documentation/LXDE>
And even those are probably outdated.
I personally didn't try lxde on mer 0.15, if you do and find that the instructions still work, please update the wiki.
If they don't and you find another way to make it work, again, update the wiki.
Thanks, I did try looking for that page but coudn't find it.
I wrote the pages on LXDE on Mer the problem is the instructions change not only when Mer updates but when some of the other packages you have to had install do to Mer wanting to install certian versions of a file. Just look for the newest version of that file and install it I guess I need to add how to find newest file to the wiki