Moving the tags to the top is /possible/ to do with css, but it would be really kludgy. If you're willing to mess around with S2 layers, it would be a lot surer to actually put the line of code that says "generate tags here" in a different place within the entry-generating function. Not sure if you want to try that?
For .poster, it might actually be easiest to absolutely position it. If you give that container "position: absolute; top: 0; left: 0;" that should slot it in fairly neatly above the userpic. Give .contents "position:relative;" to make sure .poster is contained properly. You might then have to give .metadata a left margin, but I can't say for sure yet how that will stack up once .poster is taken out of the float equation. Currently you have two floated elements plus one unfloated one all stacking up on top of each other.
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For .poster, it might actually be easiest to absolutely position it. If you give that container "position: absolute; top: 0; left: 0;" that should slot it in fairly neatly above the userpic. Give .contents "position:relative;" to make sure .poster is contained properly. You might then have to give .metadata a left margin, but I can't say for sure yet how that will stack up once .poster is taken out of the float equation. Currently you have two floated elements plus one unfloated one all stacking up on top of each other.