The last Ajax enhancement that we are going to implement in this chapter is auto-completion of tags. The concept of auto-completion found its way into web applications when Google released their Suggest searching interface. Suggest works by displaying the most popular search queries below the search input field based on what the user has typed so far. It's also similar to how code editors in integrated development environments offer code completion suggestions based on what you type. This feature saves time by letting the user type a few characters of the word they want and then select it from a list, without having to type it in completely.

We will implement this feature by offering suggestions when the user enters tags while submitting a bookmark, but instead of writing this feature from scratch, we are going to use a jQuery plugin to implement it. jQuery enjoys a large and continually growing list of plugins that provides a variety of features. Installing a plugin...