How do I show all divs in Firefox?
With jQuery;
$('div').show();
I don't know if you are asking how to do it with JavaScript or what.
Get the Web Developer Extension. Use the outline menu.
As Ben said, the Web Developer Extension.
Firebug is often essential as well.
Firebug can show the div's as you scroll over them.
In all browsers you could do something like this:
div {border: 1px red solid;}