What makes a document inaccessible?

["Brette Luck" <bluck novell com>]

Hi,

At the accessibility summit, it was mentioned that people often
unknowingly create open office documents that are not accessible.  I
know that one example of this is when people simply change the font
size to indicate that there's a heading.  What are other specific
things that users do that make documents inaccessible or hard for an
assistive technology to interpret?

Thanks so much for your time,
Brette