Google's Matt Cutts' tips on SEO

Google software engineer Matt Cutts has summed up a site review session he did at the recent PubCon in Las Vegas.
In reviewing a few sites, he gives some insight into what site mistakes a webmaster should avoid, and gives some tips on improving a site’s search engine visibility.
Duplicate contentSome of the people whose sites were reviewed had a number of different domains, and the overlapping content and pages from the various sites can cause problems:

“We discussed the difficulty of adding value to feeds when you’re running lots of sites. One thing to do is to find ways to incorporate user feedback (forums, reviews, etc.).”
“The wrong thing to do is to try to add a few extra sentences or to scramble a few words or bullet points trying to avoid duplicate content detection. If I can spot duplicate content in a minute with a search, Google has time to do more in-depth duplicate detection in its index.”

Organising contentOne of the sites Matt looked at contained hundreds of articles going back to 1996, and included a very messy sitemap page listing all the articles.

“So how should a webmaster make a sitemap on their site when they have hundreds of articles? My advice would be to break the sitemap up on your pages. Instead of hundreds of links all on one page, you could organize your articles chronologically (each year could be a page), alphabetically, or by topic.”

Having mulitple domains Some of the site’s owners had many different domains registered:

“My quick take is that if you’re running 50 or 100 domains yourself, you’re fundamentally different than the chiropractor with his one site: with that many domains, each domain doesn’t always get as much loving attention, and that can really show."
"Ask yourself how many domains you have, and if it’s so many that lots of domains end up a bit cookie-cutter-like.”

Reciprocal links
Matt spotted a few instances of sites swapping reciprocal links as a quick method of increase link popularity.

“When I saw that in the backlinks, I tried to communicate that 1) it was immediately obvious to me, and therefore our algorithms can do a pretty good job of spotting excessive reciprocal links, and 2) in the instances that I looked at, the reciprocal links weren’t doing any good."
"I urged folks to spend more time looking for ways to make a compelling site that attract viral buzz or word of mouth. Compelling sites that are well-marketed attract editorially chosen links, which tend to help a site more.”