forums and blogs SEO penalties of Google. algorithms cramping Caffeine Panda,
high-risk tactics SEO-called "black hat" trivial errors of management a website.
1) 1000 links for $25
2) Paid links on High PR website
3) Link exchange on a large scale
4) Hidden links in template
5) Profiles with artificial link with same anchor text
6) Link from unrelated languages
7) Getting too many links within short time
8) Broken link
9) Links to "bad neighborhoods"
10) Too many external links or none
11) Links hidden in third-party services (menus, widgets and counters)
12) Duplicate content
13) Contents of low quality
14) Content copied
15) Unreadable Content
18) Duplicate titles and descriptions
20) Too many ads (little content compared to the amount of ads)
21) Affiliated Sites worthless
The filters in Google
22) New domain (sandbox)
23) Multiple h1 tags
24) Keyword stuffing ("keyword density" too high)
Neither a penalty nor a mistake
In some cases, a loss of rankings or traffic volume has nothing to do with you or your site. May have changed something and this was made a sudden penalty.
25) Modify the algorithm - Google changes its algorithm, and refines the time. The main changes are called update, and sometimes involve dramatic changes in the search results. The only thing you can do is figure out what has changed and why your site does not meet the new factors as before positioning.