JavaScript: Foe of Search Engine Optimization?

For SEO professionals, the use of JavaScript has been controversial. It’s extensively applied to validate forms, detect browsers and enhance web site functionality, but anyone with some knowledge of SEO would tell you that JavaScript may hinder search engine crawlers, making part of a site invisible to search engines.

Here’s what Google says on how use of JavaScript negatively impacts indexability of a website:

“Use a text browser such as Lynx to examine your site, because most search engine spiders see your site much as Lynx would. If fancy features such as JavaScript, cookies, sessio
IDs, frames, DHTML, or Flash keep you from seeing all of your site in a text browser, then search engine spiders may have trouble crawling your site.”
http://www.google.com/support/webmasters/bin/answer.py?answer=35769nn“Google Site Search isn’t able to index content contained in JavaScript. The general rule for making sure that a web page can be indexed by Google is to ensure that all of the text that needs to be indexed is visible in a text-based browser, or a browser with JavaScript turned off.”
http://www.google.com/support/customsearch/bin/answer.py?answer=72366nnYahoo has similar statements on its inability to crawl websites which use JavaScript excessively.

How devastating could JavaScript actually be? Generally speaking, if not properly used, it may do the following to your SEO efforts:nn * It may hamper the ability of search engine crawlers to read page content.
* If used in navigation, it may prevent crawlers from seeing the links.
* It may change keyword density in your text content.
* It may change link juice distribution, page weight and PR.

Despite all the obstacles JavaScript may present to SEO, many web designers are still huge fans because it creates dynamic web pages that html codes can hardly achieve.

So if you have to use JavaScript in website development, is there any way to minimize its negative impact on SEO? Here are some tips:nn * Never use JavaScript in navigation menus and internal links which play a vital role in guiding search engines to the web pages in order to create entries for index. Obviously, if a web page cannot be crawled, it won’t be indexed. If you just want to use JavaScript to make a dynamic navigation menu, you can achieve similar but much more SEO-friendly result by using DHTML and CSS.
* Try not to use JavaScript in page content, either. Pay special attention to content text that you’ve created to achieve desired keyword density. Otherwise, keyword density could be diluted.
* If JavaScript has to be used, use “document.write” or place the script in .js files.
* If you’re not able to place JavaScript in .js files, place it unde
eath the html code to reduce the disruption that it may cause.

Bonus Tip:

JavaScript has its Yin and Yang. While SEOers suggest using JavaScript cautiously, it can actually benefit SEO by preventing search engines from crawling pages that you want to hide (mind you, “no-follows” in your meta can do some of this job, too!), such as ads, terms of use and privacy statements. You can place all these content in .js files to increase relevance of your web site.