Going to this link (validator
) I find 32 errors. Clicking "show source" in the options check boxes I run it again, but can now see what the errors are.
For example, line 21, the value you put in the "name" isn't a valid name. Below it are three links to explain what are good values.
Line 137 shows a bogas link tag (the "rel" stuff) and the links explaining it. BTW, the line number is a link to the exact code, but there is no exact way back.
Then fix 169 with the same error (and 185 and 201 and 217 and 233 and so on.
Kudos for including a nice title, but you should also include an "alt" entry as well. 508 stuff you know.
The last error is "img#wpstats..." If it is "#wpstats" then it is unique and you don't need the img element preceding it. IAC, move it to the head section.
The CSS stuff (other than the above) is fixed, but you have 4 warnings about background and border colors (that may be intended) at lines 127, 155, 339 and 695.