Two column layout, sidebar needs a background the full height of the content. I know the faux columns technique (background image on the container). Is display: table any better now, or is IE7 still the problem?
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If the sidebar width is fixed, faux columns are trivial. If both columns are fluid it gets harder. The "One True Layout" equal height trick (huge padding-bottom and negative margin-bottom) works too, but breaks anchors in some browsers.