Web 1.0 focused on commerce while Web 2.0 emphasizes user participation and contribution. The concept of Web 2.0 emerged from a 2004 brainstorming session and emphasizes tools that allow users to tag, blog, comment and modify content. Key principles of Web 2.0 include customization for individual users, focusing on the "long tail" of the web, and harnessing collective intelligence by allowing users to contribute and add value to applications and databases. Web 2.0 applications are built as ongoing services rather than fixed products, with a focus on automation, monitoring, and continuous improvement.