Node transparent to events

Is it currently possible, and if so which is the preferred way, to make 
a node "transparent" to events.
Let's say I want in my *HTML page an image overlayed to the page 
content, is there a (preferred) way to make the overlayed image 
"transparent" to events, so that the content acts as if there were no 
such image?
In the case this is not possible, why hasn't this been proposed (or - 
eventually - why has this been rejected)?
Thank you,
CAFxX