Social Bookmarking Sites

Social bookmarking is a community link sharing area. Examples of social bookmarking sites are:

• Digg
• Reddit
• Del.icio.us 
• Stumblupon

Social bookmarking your website or blog can help its page ranking (PR) by providing a backlink.  The advantage of social bookmarking is that the backlink  has been given by a human who can understand the content of the page as apposed to a spider.

You need to submit your webpage to a bookmarking site and then get people to vote for your site.  I have explained one way of doing this in the blog  Promote My Site for Free 

You need to understand whether the link is classed as good backlink and to find out this you can view the page souce of the social bookmarking site.  Find your URL link in the code and if it is tagged as nofollow then the search engine disregards it. The link is also disregarded if your webpage URL is followed by another URL.  This is called cloaking and the backlink will also be disregarded