Why Web sites do not get indexed? is a very common question raised by many of the website owners.It is necessary to follow certain factors for search engines to index your web pages. A website that seems attractive to humans, may seem meaningless to search engine robots and spiders.
Until recently, search engine were unable to read flash contents,therefore a website that had content in flash was meaningless to search engines.Similar was the case with multimedia formats. The new algorithm is capable of reading and indexing almost all the formats and scripts. Except if you have used Java Script links for your website navigation,then search engines may sometimes not be able to find your webpages.
It is suggested to make use of search engine spider simulator to check the way how search engines see your website/s.
Another reason for the website not to get indexed is an improper HTML coding.This too might avoid the search engine spiders to index your web pages.Though they are capable of dealing with minor error codes, but there are chances that they send faulty information to the search engine spiders.
It is suggested to make use of the W3C HTML Validator to check for any code errors in the HTML pages of the website.
It is equally important to carry out a survey and an indepth research on the search practices of the users.Once you know how a internet user search for your products and services,you can include those search terms and phrases in your website contents.This is known as the on page search engine optimization which helps in increasing the organic traffic to your website/s.
Sometimes, incorrect information of status codes is sent by the web servers.When requested the web server must send ‘200 OK‘. Whereas, 302 or 404 codes are sent to the search engine spiders though the website is active and functioning well with a normal web browser. Due to such responses search engines assume that the website does not exist and hence does not index the web pages.
It is very important to take care of the above mentioned possibilities when you are trying to gain better rankings in the SERP.
You may refer Search Engine Optimization(SEO): The MOST Important factor of Online Success to understand the importance of SEO.