<p>I am wondering if someone can put a bit of an authoritative reference summary of when the !important declaration in CSS does <strong>not</strong> work to override inline styles.</p>

I'm pretty sure not all browsers recognise the !important declaration. But can't remember which ones do off the top of my head. Will check and get back to you.
[EDIT]
I can confirm IE6 and earlier do not recognise !important (unless the browser is in standards compliance mode - not the default).
You can use !important to override an inline rule. But also remember that inline rules can be tagged !important as well.