JavaScript is not suitable for SEO pupose? Why?

[javed]

No JavaScript. If you need JavaScript, call it from an external file rather than dumping the code in the HTML file. JavaScript drop down menus prevent spiders from crawling beyond your homepage. If you use them, be sure to include text links at the bottom of the page...what doest it means?

[Ralph]

Search engine crawlers keep on doing changes in their algorithms.

[Jake]

Many search spiders don't execute user interface scripts, they are just examining the content they find in the raw html code, to guarantee they will find inner pages, redundant, simple html links in the footer that don;t need decoding can help.

[Arun]

Let's look at your questions one by one

1) If you need JavaScript, call it from an external file rather than dumping the code in the HTML file
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The main reason for this argument is that when putting your JS codes in separate files, browser can cache this .js files and the page loading and render time would improve. From SEO point of view I don't think it has relevance. Because even the google analytics and adsense codes are normally HTML embedded.

2) JavaScript drop down menus prevent spiders from crawling beyond your homepage.
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Usually web crawlers doesn't execute the JS code when crawling your page. So, if all of your navigation and links are created using javascript, chances are less that search engines index them.

According to google, google bot executes javascript and I've personal experience that few of my website links generated via JS got indexed in google (but not all of them). But it's preferred not to use javascript for your COMPLETE site navigation because it's up-to the crawler to execute them or not.

3) If you use them, be sure to include text links at the bottom of the page
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This is what I explained in the last sentence. If you are creating all of your navigation in javascript ( for look and feel or interactive pages), you can add links at the bottom so that crawlers that doesn't execute JS will not miss your links.