nomis5 - 8:53 pm on May 9, 2012 (gmt 0)
I agree with the last poster, Google couldn't give one jot if your code is tidy or not.
More importantly, they can't determine if you code is spaghetti junction code or the latest compliant code.
There is a big BUT though. Life on the web is changing so quickly that good quality standard code using CSS has almost become essential in medium to large websites. Spaghetti coded websites take eons to change sitewide and you need to be able to do that quickly and efficiently nowadays.
I'm in the process of changing one of my smaller sites to clean and tidy CSS at the moment because I intend to expand it considerably over the next six months.