IBP is a crap. If you take a look at any top website now a days, they are not perfectly optimized and in IBP their overall percentage will show as 10%, but they are ranking no1. Now-a-days backlink plays important role. How is your website optimized , do not count in view of google. For example in IBP it says validation of web page plays a important factor, but a lot of top ranking website are not validated for example google.com.
If you validated google.com, it has 40 errors.
Same as yahoo.com, facebook.com, myspace.com etc..