What is link wheel and how it is useful in SEO??

Link wheel is together connected new blogs/pages of web 2.0 properties such as livejournal, bloglines, soulcast and etc., all these web 2.0 properties must have a backlink to Your money site, not only to each other. This mini sites have unique articles or only one article with all these backlinks. When web 2.0 properties link to each other and to Your money site, You get much more link juice, because every authority site send power to next one and next in this way making more powerful backlinks.

What is a Sitemap and How is It Useful in SEO?

site map is like a map, it eases of the burden of users and crawlers when they try to locate your complete website. for humans html site map is used and for crawlers there is xml sitemap...