Over-wide graphics

[Dominick Layfield]

Quick question:

If I have a centered graphic (inside a float environment) whose width is 
greater than the text width, it seems that the centering mechanism 
breaks down.

What happens is that the left edge of the graphic gets aligned with with 
the left text margin, while the right edge sticks out beyond the right 
margin.

What I want to happen, and what I think should happen, is that the 
graphic should extend equally beyond both margins.

Can anyone offer advice on how to achieve this?

Thanks,

XOX DOM