I really enjoyed this post by donna, so I thought I’d put together my own favorite five, based on what I’ve seen over the years:
1) Renaming pages or moving them to a different directory location without putting in 301 redirects (this is by far the most common and worst of all mistakes)
2) URL spamming (by choice or by accident)
3) Redesigned website/homepage with a flash intro page – but it looks so cool!
4) Relying too heavily on one type of inbound link (playing the cat and mouse game with Google)
5) Moved to a new webhost and forgot to also move the robots.txt and/or .htaccess files.
Many of these items could easily be avoided if the website owner retained the services of an online marketing consultant.