This started out as a programming "widget" in the Macintosh interface; you clicked on the first item and a list dropped down like a window shade.
These menus tend to cover up material underneath them, making it difficult for visitors to see clearly on your site. They are best used to make "choices of kind", since you can only see the first item; for example, the category is "shoes" and the dropdown menu contains kinds like running, cross-training, basketball, tennis and so forth.
Sometimes, website designers take an element that serves a particular purpose (like a dropdown menu) and then use it "creatively." The best way to make sure that all of the elements used in a web page help you to make the conversion is to get a website evaluation.
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