While converting a desktop application to a web app, I’ve run across my ignorance when attempting to implement a multi-column data entry form using CSS. I’m resolved to avoid using tables for this type of thing, and while I found a good reference to laying out a data entry form, I can find nothing that applies to multiple-column layouts like this one:

Can anyone point me in the right direction?
Here’s a screen shot, please notice how I demonstrated the tab order with numbers:
Please note that
RedFilter'sanswer has a different tab order, which I have demonstrated in the screenshot below:(code below complete with ASP.NET validators)
CSS (cross browser friendly)
HTML