In the Google Webmaster guidelines for optimisation it states that the web designer/builder must ensure their html is of high technical quality. We can only guess what this means. After reading this I decided to run my pages through the W3C parse checker and sure enough, loads of errors. I decided to correct these but at the same time I decided to convert my pages from html 4.01 transistional to xhtml 1.0 transistional. My new pages have not been cached by Google yet so I guess I will see the affect of these changes in the next 2 or 3 months. Will let you know if it has any significant affect on my SERPs. So, are you guys using html still or have you moved to xhtml yet? Also, what else do you guys think Google is referring to when they mention "technical quality"?