Today, in the middle of the ?rst decade of the 21st century, the Internet has become a major communication medium, where virtually any kind of content can be transferred instantly and reliably between individual users and entire - ganizations located in any part of the globe. The World Wide Web (WWW) has a tremendous e?ect on our daily activities at work and at home. Consequently, more e?ective and e?cient methods and technologies are needed to make...