Today, Google Webmaster Help releases new videos discussing the two meta attributes that lets you prevent the “link juice” from your site to flow to other unknown external sites and preventing your website to be crawled and listed on Google’s result pages.
The first video discusses the reason why an uncrawled URLs are still on the search result pages of the said search engines despite the webmaster prevented the spider crawling thru robots.txt. Solution provided by Matt Cutts was using the NOINDEX attribute for the meta robots tag on your header so that the pages on the index will be dropped from their list. Here’s the video:
This next video discusses the nofollow attribute to control or deal with comment spamming. It is explained by him again how the owner of sites makes their own solution in avoiding this kind of spamming. However, there’s no detailed information on the video that is saying how Google deals with comment spammers. Watch this video: