I don't see the problem with using positioning, neither relative combined with floats or absolute. And, i would certainly not say that many newbies use AP for everything, actually many newbies wouldn't even know to apply the relatively positioned container technique, rendering their use of Absolute Positioning very limited.
As for cross-browser compatibility, i can't say its much more of an issue then when dealing with floats, and that's only when we target outdated browsers such as IE6 and earlier, all updated browsers works as intended.
Some web designers have even gone as far as to say floats where more flexible, which would only be the case when blindly supporting older browsers. You likely want to ditch support for such browsers, to enable features such as true min-width, and png alpha transparency without having to apply hacks anyway. Transparency is also very likely to become increasingly more popular with web graphics designers and/or web designers, as the web designer figures out how to make full use of it.
Creating a 3-column layout which works in all browsers, can be done equally easily as using AP, with about the same coding required, it more or less depends on what you want done, and that's only from my current experience.
For example in my experience, layouts with a footer are harder to deal with when working with pure AP, you either need to stick it at the bottom of the center column or do without. But as layouts with a footer that spans over multiple columns are quite popular for some reason (maybe because they are hard to make), float may be a more suitable choice.
This is only because the positioned columns are removed from the normal flow, so that the wrapping container stays collapsed, there might be a solution to this, its however not known to me yet.
In a float based layout, we got 2 options as of how to keep the footer at the bottom of the highest column, which I'm making an example of right now. :-)
But anyway, that's just in my experience, maybe someone else has found a solution to the footer problem in AP layouts.
But to give an answer on the post, i would assume that keeping the
Content column before the
left and
right columns, would give search engines easier access to the content, without polluting it to much. This is both achievable in AP and float layouts.
The
Content column would still be centered between the
left and
right columns visually, but would be placed before in the code.
As for keywords, its a good idea to link your pages, both for users and search engines, so having lots of content links to other internal pages would be good.
Instead of me debugging the suggested css, try to check out the links in my sig, there should be some of the best examples. Even though i doupt that the placement of the center column in the code wold matter much in practice, some of the layouts has been constructed that way, including the float based equal-height column layout.
It is more obvious how to do that in AP based layouts, so that may be why some suggest it as an advantage. Some playing with the floats, and use of relative positioning however gets it working in float layouts as well.
