Google Chrome version 23 just released overnight now includes a very useful ruler in web inspector mode. It’s one of those tools that I always needed, but never realised until now!
If you are a web designer or developer, restart your Chrome now for the new feature.

New bug coming with that new chrome version: Native chrome dev tools are now slower than before
I hadn’t noticed the speed decrease, will have a look.
I’m noticing it a lot on my MacBook while inspecting a fairly large web app. To the point where the whole thing locks up for 5-10 seconds.
It happens a lot when expanding and collapsing tags. It is also really slow when a lot of the inspected CSS changes from a hover.
And those rulers are REALLY annoying if you want to align things in those first 8 or so pixels. Is there a way to remove them, because I can’t find one.
Too bad I’m forced to use Chrome for this. I’d much rather use Firefox.
Hopefully the chromium team will adress this issue.
Anyone know how to turn this off? This has to be the most annoying thing. Honestly speaking, if I wanted a ruler, I’d go get an extension for it. The fact that chrome force-fed me a ruler in my dearest element inspector has put a sour taste in my mouth.
Hi Brian, you will be glad to know a setting has been added in the latest Webkit build.
I hope my reading of this is correct:
https://bugs.webkit.org/show_bug.cgi?id=101554
Sure, they can be really useful. But they can also be extremely annoying and get in the way. It’s really frustrating that there appears to be no way to turn them off!