It's very easy to screw up your own SEO, and if you've hired someone else to do it for you, that doubles the anguish when they also make these sorts of mistakes. (You just paid for it!)
Whether do it yourself or hire your SEO out, you have to be aware of what not only just doesn't work, but also what may indeed be counter-productive, and harm you even more.
Let's examine 5 ways SEO mistakes can happen, and how they can be avoided.
5 bad SEO mistakes you'll want to avoid at all costs!
Misusing keywords and anchor text – Today the Google algorithm has wised up to the point where it can sniff out attempts to game the rankings with keyword manipulation from a mile away. The best practice today is to use keywords naturally on your pages, utilizing related keywords and synonyms, and diversifying your anchor text accordingly, using natural combinations, naked URLs, and some generic terms like “click here”.
Avoid using Tags – The primary reason you'll need to avoid the use of tags is that they automatically create a duplicate content issue for you. Use categories instead. And if you use a tag cloud you've only compounded the problem by using valuable front page real estate as well.
Using Flash on your pages – While this may be necessary to achieve some sort of visual effect you'd like to use, you should ask yourself if it's worth it, as it can be bad for SEO and how well your site renders in mobile.
Not optimizing for Mobile – Since over half of all web users now get here via a mobile device, you need to make sure you recognize and account for this. Google also now devalues unresponsive pages in search with the label that your page “May not work on your device”.
Poor internal linking – The spate of recent Google updates has made this one of the last bastions of effective on-site SEO that really works well. Strive to make your site user friendly in this respect, and this is one area to not be shy about using keywords. (With prudence and diversity, of course!)