One thing that has to be considered when narrowing the journal width, is that if the entries contain pictures or meme's, they will stretch the journal to fit them in the entries. Doesn't matter what percentage/pixel value you put as your journal width, the journal entries will always remain at least the width of the picture it contains. Now I myself am a major picspammer, as are several people on my f-list, so to prevent my journal from stretching, I added scrollbars to my entries, so if a large picture or meme is posted, it will automatically be put under a scrollbar.
Scrollbars in entries tutorial
I tested this by replacing my existing code with Kunzite's new code in my bimma journal, added the above scrollbar code immediately after that, and it's working fine. :)
Just pointing this out, since I myself am one of those HTML challenged-types, but I still want to be able to customize my journals. Seeing as, back when I tried to narrow down my journal width, it of course didn't work, due to the whole picture/Meme stretching thing. As soon as I figured what the cause was, I looked up the scroolbar tutorial and added that code to my layer, which fixed the width problem.
Hope somebody finds this useful :)