Big improvements to debugging styles.

The debugging styles are a lot more informative. There's basically two working modes which all work through contextual hovers. Not hovering anything will leave the page layout intact.

Hovering over the body will illustrate all the grid containers with a red tint, background columns and column rulers. It will blend in with the page design so you can see how everything lines up with the grid in a way that's not too distracting.

The second mode is triggered when hovering over a grid container. It will show all the grid elements (faint shade), prefix/suffix padding (purple shade), push/pull (generated label above the element) and alpha/omega items (faint purple dot on their respective edges). In this second mode, the container ruler from the first mode disappears but they will show for each element with a grid class applied but only on hover.

A few more notes about this second "container" mode:
- It will warn when a push and pull class is applied to a single element.
- Grids nested within grids nested within grids are a bad idea. Two levels deep of embeded grids will show a 2 pixel grey dotted outline. Starting from the third level It will progressively show a thicker red outline to give you a warning.
- The background and foreground colors are set to a neutral tone so your page design doesn't get in the way of showing you all of this useful information.
- Background images are stripped. This couldn't be helped since they cannot be faded without an opacity change of the container but that leads to bigger consequences.

It's very clean in its presentation and I've tested on a lot of pages. I've spotted a lot of mistakes too out in the wild which I think shows how useful these debugging styles can be. If you want to test it out for yourself you can try these bookmarklets. That link also contains a demo/test. I made two versions. One for the Drupal specific implementation and the other works with the source 960.gs. Only differences is the hyphen- vs underscore_.

And forget about IE. Very basic support for that crummy browser. The latest shipping versions of Firefox, Chrome, Safari and Opera work nicely though. Uses a lot of CSS3 selectors and properties.