1) Website should not have much Flash contents. Because all search engines cant able to recognize or read flash contents. Instead if your website has Text contents then the chances of being in top 10 of all search engines are more.
3) We can’t rely on META tags. As Search engines like GOOGLE dont measure your website from META tags.
4) We cant put keywords of our website in such a way that user cant able to see. like, Hiding them using same color as of your page color.
5) Don’t get own website content Texts from another website by just doing copy/paste. This will not help to improve website rank in search engines. It might happen that google may block your website.
6) We can’t use Bad keywords, or low density keywords related to our website. Also we cant use keywords that are not at all goes with the theme of our website.
7) Don’t put important Headings of a website content texts in form of image. Instead put important headings into <H1> tag. As search engine gives much importants to these heading tags of HTML
8) We can’t leave images residing in our website without any proper keyword based ALT tag.
9) Website taking more time to load because of messy coding and improper structure of code.
10) Having TITLE tag without using important Keywords.
11) We can’t build our website without having Internal links and most importantly Sitemap of our website.
12) We must avoid Inbound links from websites having very much low page rank nearly 0-1.
Hope it Helps you to optimize your website Better.