Don’t make changes that are not user friendly as that will affect the popularity of your site.
Don’t make or use duplicate content as they too affect your site ranking.
Don’t use such parameters which become your pages permanent URL structure.
Don’t create a page which is not any of the page on your site or its parent page.
Don’t use multimedia to develop or redesign your site. It affects the loading speed of your page and will affect ranking of the website or webpage.
Don’t let a page exist with the error 404 (file not found).
Don’t make it complicated for users to search the categories. Provide them with a click path.
Don’t give away links of your site without any good enough reason.
Don’t always rely on top-down navigation to direct users to your content.
Don’t let your content appear in pop-ups.
Don’t use easy SEO
techniques for coding that are less optimal.
Don’t use splash pages.