How often do google spiders read the sitemap?

[trustdnb]

I have a few questions about sitemap xml and would appreciate if you guys can answer them for me

1) what is the difference between xml and html sitemap? which is more benefit for SEO?
2) How long does it takes google spiders read the sitemap
3) can you request google spiders to read your site upon request?
4) What should be in the sitemap?

Any tips or advice on how to achieve a good sitemap would be most appreciated

Thanks in advance.

 

[expmrb]

1. .xml sitemaps are for search engines to crawl and index your sitemap. And, html sitemaps are for users who are visiting your site for proper navigation.
2. There is no fixed time for google spiders to crawl your site. It depends solely upon the facts that how much quality inbound links you have and how frequently your site gets updated.
3. You can submit your new or updated page urls to Google through Google Webmasters tool via 'Fetch as Google.' It will fasten up the process a bit.
4. Which sitemap you are asking about??