1. Web designing: One of the most common of the mistakes that occur is in the designing of the websites or rather the incorrect designing of the websites. If there is any inadequacy in designing the website, for example; lack of proper navigation, using frames to save web designers designing times, and large graphics which takes more time to load, these all makes effect on listing in Search Engine. It can also happen that the search engine spiders may get blocked from crawling the sites that are not well designed. It is also seen in many sites, images and other script languages are used for giving fine looks. These are good but not crawl-able by the search engine spiders. This should be avoided as far as possible. Another thing that also creates problem is the large images. They cause more time to download page, people don't have time to wait for long time. Make your images in more pieces so it will take less time than single image. Therefore it should be tried to make low resolution file where high-resolution graphics are not required. If it is essential to use large images then it is better to use thumbnails and open it in separate page. This may give additional benefit of creating more pages and more text. Therefore proper web designing is very essential part of Search Engine Optimization.
2. Content: Content also plays a very important part in search engine ranking. For the search engine spiders and search engine directory users the clarity of the content is also very important. If the content is not well written and not relevant, or even if they are not updated periodically then it can be said that the site is neither search engine friendly nor user friendly. This will definitely affect the ranking of the site. Therefore there should be well written contents and also must have targeted keywords and phrases. This is the key to high ranking.
3. Duplicity: It is strongly recommended not to copy contents from other websites. The fact is that if your site is updated later and the search engine compares your site with others and find that you are using replica of other contents then it is sure that your site would be charged of spamming and may result into penalty or low ranking of your site.
Therefore it can be seen that these thing can harm your ranking on the search engines. Not only these but there are also other such mistakes that occur very often that have a negative effect on ranking your page, which we shall discuss later on.