A copy of a post I made in the Joomla! forum:

I was having issuses with the styling of my footer.
Basically, it seemed that it wanted to use a different style rule "normally", and when I had an error "you are not permitted to view this content".

Looking at the generated code using FireBug, I saw the reason - The structure was different, and the "correct" style rules were being applied...

Here is what I see at the end of the FireBug HTML output.
When I have no problems in the page:

<div class="body">
<div class="container">
...
</div>
</div>
<div class="footer">
<div class="container">
...
</div>
</div>

When I have the "no privilege" error
<div class="body">
<div class="container">
...
</div>
<div class="footer">
<div class="container">
...
</div>
</div>
</div>

There seems to be a shift in the </div> tags