If you haven't played with Chrome OS yet, it has one fundamental niggle that harkens back to the DOS days of yore: windows don't exist, and it has no way of displaying multiple tabs on screen at the same time. This means if you want to refer to a document while you compose an email, you need to repetitively switch between tabs -- and I think we can all agree that tab-switching is one of the most important omissions from the Universal Declaration of Human Rights.Chrome OS does support one way of displaying multiple Web pages at the same time, however: panels. If you've looked through our Chromium OS galleries (or taken a quick look at the screenshot above) you'll notice some always-on-top panels across the bottom of the screen. Panels are handy things -- capable of being resized, or quickly popped down out of view. By default, the download manager, popped-out Gmail chat windows and the media player display in panels -- but, for some reason, there's no way to load custom websites in panels.Which brings us onto our very first Chrome OS-specific extension: Panelize. With Panelize you can put anything into a panel, such as Gmail, Reader, or even Download Squad. In one fell swoop, having to switch between tabs is a thing of the past! Realizing that full-size websites don't look very good in small panels, Panelize lets you pop open mobile versions of popular Google services, like Gmail, Docs, Reader and Voice. If you look at the screeshot above, you can see the mobile version of Reader in a panel -- pretty darn cool.Read more: DownloadSquad