What is Zotero?
Zotero offers free online reference management and authoring. The Firefox extension is designed for the Firefox browser (Mac and PC), and a version is also available for Chrome and Safari browsers. It allows you to easily save snapshots of webpages (useful for capturing the website as it was when you viewed it), and is very efficient at pulling out the relevant citation information for a website. Zotero allow you to access your saved citations offline and to share resources with group members.
Comparison with other referencing tools
Zotero is very efficient at pulling out the relevant citation information from a website.
For more a more detailed comparison, use the Comparison Chart (University of Wisconsin-Madison)