For w3 total cache users, if you have duplicated content notification in Google webmaster tool, read this W3 total cache slash url problem fix.
Have you looked how your blog’s appearance in some browsers? check this post about if your blog looks different in browsers (ie or firefox).
There is no attribute “target” HTML strict solution and fix
Thesis is the best SEO wordpress theme 2010.
A Video guide on how to fix or correct the validator w3c error codes by cleaning up a small simple coding mistakes in our wordpress blog or website