The various programming languages used for web page building....
JavaScript
JavaScript is a programming language that allows web designers to create dynamic content. However, it’s also not necessarily SEO-friendly. In fact, JavaScript often completely halts a crawler from indexing a web site. To overcome this, many web designers externalize any JavaScript that’s included on the web site.Externalizing the JavaScript creates a situation where it is actually run from an external location, such as a file on your web server.
Flash
Flash is another of those technologies that some users absolutely hate. That’s because Flash, though very cool, is resource intensive. It causes pages to load slower, and users often get stuck on an opening Flash page and can’t move forward until the Flash has finished executing. Flash is also a nightmare when it comes to SEO.
Dynamic ASP
These sites don’t change beyond the regular updates by a webmaster. On the other hand, dynamic web pages are web pages that are created on the fly according to preferences that users specify in a form or menu. The problem with these sites is that they don’t technically exist until the user creates them. Because a web crawler can’t make the selections that “build” these pages, most dynamic web pages aren’t indexed in search engines.
There are ways around this, however. Dynamic URLs can be converted to static URLs with the right coding. It’s also possible to use paid inclusion services to index dynamic pages down to a predefined number of levels.
PHP
Search engine crawlers being what they are — pre programmed applications — there’s a limit to what they can index. PHP is another of those programming languages that falls outside the boundaries of normal web-site coding. Search engine crawlers see PHP as another obstacle if it’s not properly executed.One thing that works well with PHP is designing the code to look like HTML. It requires an experienced code jockey, but it can be done. And once the code has been disguised, the PHP site can be crawled and indexed so that it’s returned in search results.