Websites engage in search engine optimization in order to gain more visitors via search engines. But website owners need not only consider attaining new visitors but should also focus on making the old ones want to come visit back. In no particular order, here are the list of what may be considered as "common website mistakes" that can be a turn off for many visitors and errors that hinders a website from being easily indexed by major search engines. This list primarily deals with the web design aspect of a website.
1. Bad website design. First impression lasts, this means that even though your website may possess good content, visitors may be forced to look for another website the moment they see how bad or disorganized your content is displayed. A good example of a bad design would be poor text and background color combination which may cause eye strain for most visitors.
2. Page Not Found. Also called error 404, this type of error comes up when a link connects to a web page that was either moved to another location or completely removed or simply connected to a incorrectly typed URL. This can become annoying to some visitors. What website owners could do is instead of displaying a dull Error 404 message, they could redirect it to a sitemap or search page where visitors could look for the information they need. SEO wise, error 404s can be redirected to a page that needs boosting.
3. Server not found. An error that could cost money for a commercial website, this can be taken about by unreliable web hosting. Website owners should consider the uptime capacity when choosing web hosting services.
4. No meta tags. Although search engines have lessen their reliance on meta tags in terms of indexing websites, a good web design should be complete with meta tags since they help search engines to easily categorize a website. This helps boost a website's rank on targeted keywords.
5. Non SE friendly URLs. Having targeted keywords on the URL not only helps in search engine ranking, as opposed to dynamic ones (URLs with random alphanumerics and symbols), a search engine friendly URL is also easier for visitors to remember.
6. No search box. Most of the time, visitors would use the search box of a website when they could not easily find what they're looking for. Having one that is not functioning, or having none at all, may cause a number of visitors to look for another website.
7. Poor navigation / usability. Just as having no search features, poor navigation or user interface may bring confusion or difficulty (and annoyance) to visitors.
8. Flash / no alt text on images. Flash not only has issues with search engines in terms of indexing, it may also cause difficulties to visitors since not everyone has hi-speed Internet connection. Flash may take time to load and may cost a number of visitors as a result.
9. Domain Name. Having a good domain name is one of the characteristics of a successful websites. Basically, the easier they are to remember or the closer they are to targeted keywords the better. The only problem is that most of the strategic domain names are probably taken or being sold at very high prices. Website owners could innovate by using prefixes such as "my" or "the" on their domain names. Long and confusing domain names should be avoided as much as possible.
10. Pop up ads. Probably one of the largest turn offs for a website, pop up ads are just basically annoying to most people. Websites may want to avoid or at least minimize in engaging with pop up advertising.
These common website mistakes can be preceded with careful web design and a little knowledge in search engine optimization. Not necessarily saying that having prevented all of what is listed above will surefire a website's way to success, it is still good experience to be well aware of what is considered to be common mistakes that websites commit.