Virtually every site I’ve worked with in recent years has had need for dependent drop downs of some nature.
Usually implementing a dependent drop down consists one of two options: Outputting every option into a JavaScript method, or invoking an Ajax call to get the next set of options. The disadvantage to both of these options is usually a bulky mechanism the developer must write in order to provide a simple UI component.

Salesforce provides a dependent picklist feature, which in keeping with their no-software mantra, eliminates any need for a custom ajax or javascript solution. Define a dependent picklist and reference it in your page layout or Visualforce page. Salesforce takes care of everything else under the covers.

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