To move the Right Sidebar in Left side in Twenty Ten themes in WordPress, Then just open style.css stylesheet and in the last of this CSS file, just add the following few lines. Now the right sidebar with all the content placing into that will be transferred into left sidebar.
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/*Move Right sidebar to Left*/
#container { float:right; margin-right:-260px;?? ? ? ?width: 100%;}
#content { margin: 0 280px 0 20px;}
#primary, #secondary {float:left;clear:left;margin-left: 10px;}
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Enjoy!!