In the beginning there was just HTML and life was simple. The web pages were largely text based and the search engines that were designed to copy, index and rank these web pages were also HTML-based. There was no conflict of codes and everything was fine as far as web design and SEO were concerned.
Then came the design invasion with its arsenal of Flash, Java Script and DHTML. Web content got a complete make over and it won the media rave reviews. But all was not hunky dory. The new codes confused the search engine spider, which had no idea how to go about tagging and indexing these new entities. As a result many of the pretty pages never showed up in searches and the very purpose of web pages was lost.
However, web pages continue to be pretty and easy to find. How did that happen? Did the search engine change?
Not really. What happened instead was that these pages started making themselves accessible to the spider. Here are the techniques, which are now common.
The first is to limit java script usage. Use it as an external file and do not put it on top of the source code page. The top of the source code page is what the spider looks at first, if it finds java there, it will back off and your page will not show up in a search. The same holds true for pages built using CSS.
With Flash, Shockwave and Streaming Video, it is even worse because the spider cannot even find the source code. It is useful to build hybrid pages where at least a part of the page is in HTML. You could even limit it to just the navigation bar but it will give the spider at least something to index. Hyperlinks should not be merged with flash components.
Another useful technique is to submit workaround pages to the search engine. What happens here is that a separate page, HTML-based, carrying important sections on the site is given to the search engine. In fact each important section can have a workaround page.
Search engines cannot index text that is part of a graphic. What you need to do here is copy the graphic tag placed in the ALT tag. Pages that require registration, cookies or passwords are also a big no no with spiders. Acrobat files are another big block though Google has modified its program to spider Acrobat files, popularly knows as PDF files.
Finally, web addresses that are full of question marks, ampersands, equal signs and a lot of other symbols scare spiders. Some search engines like Google, Altavista, FAST and Inktomi have modified their programs to tackle this, but most have not. So, avoid using them.