As a general rule of thumb it could be said that in order to be listed in the search engines, you should prefer content that in HTML text format. Images, Flash files, Java applets, and other non-text content is often ignored or devalued by search engine spiders, despite advances in crawling technology.
Few major obstacles are listed below.
At least Google’s crawler can submit web forms, but it generally doesn’t do it unless it can detect a good reason to do so. Search engines are continuously improving in this respect, but still the best possible results are ensured by not hiding any major content behind submit buttons.
There are all kinds of unwanted bots on the web – we are not talking about search engine crawlers, but other more malicious or just useless pieces of software trying to extract information from your website. Webmasters can restrict these kinds of bots from accessing the page by using the meta robots tag and robots.txt file.
This might be unintentional consequences, however, and these might also block the crawlers. So, be careful when using meta robots tag and robots.txt.
An iframe (short for “inline frame”) is HTML syntax that allows you to embed web page within another web page, so it’s basically a page within a page. The technology makes it easy to create quick solutions for integrating two websites with each other. YouTube uses iframes in its video embed code.
Google bot can index the content in iframes, but the credit of the content always goes to the original page (that is being embedded) and not to the page that displays the iframe. So, if you rely heavily on iframes on your website, this will probably have negative impact on your search engine ranking.
One fairly popular way to include video objects on a website is Adobe Flash. Flash makes websites look nice, but it’s bad for search engine optimization and universal web standards. What you gain in eye candy you lose in search engine ranking and usability.
First of all, Flash can make a page painfully slow to load, which is always bad for SEO. Search engine crawlers also have trouble reading and interpreting the content presented in Flash objects. Google tries its best to extract information, like texts and links, from Flash objects, yet even that won’t always work. Websites build with the Java programming language suffer many of the same problems as Flash-based websites.