Its not a bug in mojoPortal if you have problem with a skin and your question is not at all related to the topic of this thread which is FCKeditor so it would have been better to start a new thread in the skin forums than opening up this old discussion again.
Sounds like a timing issue where the CSS or javscript is applied after the page loads and you see some visible movement as the style is applied.
I'd suggest make sure you are not using a debug build of mojoPortal as that could be just enough slower to load to make an issue like that happen. I would also make sure you have caching enabled for the CSS.
At the end of the day mojoPortal just delivers html and CSS and javascript to the web browser and the browser does the rendering, any visual issues would be solved by changes to the markup, CSS, or custom javascript.
Hope that helps,
Joe