There are lots of great lists out there with advice about mistakes you can make with your SEO.  But NONE as big as this!  I thought it would be fun to compile the biggest, baddest, most complete list there is.  (Be sure to read #102) That’s a huge bonus…

101 SEO Mistakes

Enjoy! (these are in no particular order)

The first 10 are from Alhan Kesar’s too funny post: Ten ways to piss off your SEO

1) Forget to place a robots.txt file on the dev server. It’s great that Google is already picking up pages and that our dev server is ranking for “cute puppy clothing”.
2) Link to www and non-www versions of a site. Search engines are great at figuring out which version of a url to use. No need to worry about a stupid prefix.
3) Use tables instead of divs and place sidebar coding above page content. I really love it when the first 200 words on an html document are just links to other pages. And I especially like it when all you see are a bunch of table width attributes, colspans,
’s and all that good stuff. Reminds me of the old days.
4) Incorrectly set up a 404 page so that any url gives a 200 status. Google loves it when it checks to make sure that your 404 pages do indeed display a 404 status and finds that in fact your server is totally okay with nonexistent urls. That doesn’t look fishy at all.
5) Link to different pages using the same text. We have 10 pages on our website about “free poker”. Let’s link to them all with those words so that users can really see the difference between each page!
6) Create a sitemap that uses images as links instead of page titles. Rollover images are a great way to make a sitemap truly captivating. Also, add some Ajax action in there to make it more interactive.
7) Create urls that say nothing. What could possibly give more insight to a user about a page than the following url: www.mybadasswebsite.com/webapp/wcs/stores/servlet/category1_10251_10201_12559_-1_12551
8) << that’s an 8… Link to the /index.php page from all pages on a website. You cannot imagine the joy that I feel seeing high PR given to the /index.php page. It makes me proud to know that both versions of our home page are doing great.
9) Use an entire paragraph as a link to another page. This is an awesome way to pack a lot of anchor text keywords into one link…
10) Use H1, H2, H3, or H4 tags in navigational menu links. I love seeing the same H1 tags used across an entire site. It really gives it that consistency that I look for.

The rest are from me and my experience as well as some great lists I gave credit to at the bottom of the post:

11) Change your content without consulting with your SEO
12) Buy spammy links during the SEO campaign
13) Use: User-agent: * Disallow: * in your robots.txt
14) Install a shiny new Flash navigation system
15) Move the site to a new TLD
16) Leave the title tag empty
17) Put the top 100 keywords you want to rank for in the META keyword tag
18) Leave the keywords out of the content
19) Use images for headings rather than h1-h6 tags
20) Use a ~ as a word separator in your urls (yes I have seen this very recently. Huge e-commerce site to boot.)
21) Create 50 new pages that all say the same thing except the city or other geo info is different.
22) Use “click here” for anchor text. Adobe appreciates it trust me
23) Keyword stuffing. Using the keyword on the page 30 times and in every sentence is not going to make you rich.
24) Think about SEO after you launch the site
25) Target general keywords. Good luck reaching #1 for “shoes” or “cars”
26) Duplicate title tags.
27) Making the company name the FIRST thing in the title tag. This rarely is the best approach.
28) Create a blog and then fill it full of advertising only posts or links to your site
29) Create a blog then don’t ever post. EVER
30) Get links from every Tom, Dick and Harry site out there. (Even the relevant ones!)
31) Build a “Resources” page and fill it full of links to every Tom, Dick and Harry site out there
32) Use the same anchor text for every dang link to your site
33) Check your rankings everyday and fire off the morning panic email to the SEO
34) Don’t start with keyword research.
35) Submit urls that have the wrong case.
36) Don’t use a custom 404 page
37) Create 100’s of blog sites and link them all together for lots of link juice :/
38) Build links too fast. Google is watching…
39) Think SEO is a free traffic source. Do you think the websites on top got there without time and investment?
40) Write content that is only optimized for the engines, not human friendly too
41) Talk about the “other” SEO that can get you on the first page of Google by the end of the week
42) Target the wrong keywords.
43) Use nothing but images as content on your home page
44) Have content automatically populate your blog from other blogs
45) Skip analytics, hell who needs that?
46) Put distracting links near the call to action
47) Put an h1 at the top of the page, fill it with keywords and use CSS to make it tiny
48) Put an h1 at the bottom of the page with lots of h2’s and h3’s above it
49) Use a slider with html content and every slide has an h1 with varying content. Guess what, it’s all in the home page code.
50) Do SEO yourself, then ask us if it’s right
51) Use URL’s that are 5 levels deep
52) Create a blog or website on a domain you don’t own.
53) Use unfriendly file names
54) Use unrelated or not optimized alt text on images.
55) Use the Google toolbar to count back links, you may be missing a few
56) Email Google and ask them to review your site for terms of service violations. DOH!
57) Create a site with nothing but affiliate ads and link it to your main site
58) Copy someone elses content and put it on your site
59) Use URL re-writing that does not include keywords.
60) Build your new site using 100% Flash…I could put an example of an invisible site here but I wont!
61) Tell us you “know SEO”
62) Use only the company name as the title tag
63) Try to convince us all you need is Social Media
64) Give up after the first month
65) Offer us skunk beer in return for SEO
66) Offer us “a piece of the pie” because your product is the “nest big thing”
67) Chase unrealistic keywords for your budget. $100 a month will not get you ranking for “Viagra” anytime soon
68) Duplicate the META descriptions so Google will grab some random useless garble to show your customers in the SERPS
69) Focusing on link quantity versus quality
70) Commenting on blogs that get moderated and then not following up to see if they get approved
71) Getting site wide footer or sidebar links and counting each link
72) Redirecting all 404’s to the home page
73) Making your home page nothing but links. Me thinks that may be diluting your PR slightly
74) Using tons of inline CSS and Javascript
75) Serving different pages to target humans and spyders
76) Filling comments in the code with keywords
77) Hiding keywords in content by using the same color text as the background
78) Assuming that the keywords you are targeting are just as popular today as they were 2 years ago
79) Take others advice without first consulting with your SEO
80) Trying to stay completely removed from the process
81) Don’t pay us
82) Blowing off Bing and Yahoo.
83) Thinking Social Media is a fad
84) Asking us, “what is Twitter”
85) Telling us you were ranking just fine earlier this year for that keyword
86) Go ahead, bold your keywords EVERY FRICKIN TIME it appears on the site
87) No, it doesn’t help if you use the keyword more than once in the title tag
88) Tell us page load speed doesn’t matter
89) Ask us to spell “canonicalization” 🙂
90) Delete a page without 301 redirecting the url to a new page
91) Use a Flash splash page.
92) Use session ID’s in the url, Google loves those. Also, don’t worry about their parameter handler in Webmaster Tools.
93) Create tons of sub domains vs sub directories.
94) Create content with no links to ANYTHING
95) Don’t put images in your content
96) Be impatient, it will happen but not tomorrow!
97) Optimize your homepage for every keyword under the sun
98) Ignore site structure, the engines read the code from top left to right and down. Have you looked at it lately?
99) Disregard traffic analysis, there is NO WAY the traffic increase is because of our work
100) Blame lack of conversions on us, even though traffic is up 30%
101) AND one of my all time favorites: Hiding content in a container 1 px X 1 px…gotta love it

(Bonus 102!)
102) Linking to SEO related blog posts you find useful and a little entertaining 😉

Some awesome posts and lists I used to compile this list:

Hope you enjoyed the list! I’m sure I missed some so please leave them in the comments below. I will add them to the list if I like them.