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An advanced graphical technique found on Web pages. It is used when a Web designer wants a graphic to change when an event associated with a mouse occurs. A common use of rollovers is to provide a visual indication when a mouse pointer is over an area of a graphic which has a hyperlink associated with it. For example, the graphic might be a map with a number of cities whose names change colour when the mouse traverses the area associated with a hyperlink. Rollovers can be associated with a number of mouse events such as a mouse being clicked down, being clicked up, or being moved outside the area of the embedded link. They are created by using a simple scripting language such as JavaScript. Programming statements in the language are embedded in the HTML code of a Web page: these statements sense when a mouse event occurs and change the graphic associated with the hyperlinked area. For example, changing from a graphic which has a name displayed in one colour to a near identical graphic where the name is displayed in another colour. Rollovers can be programmed by hand but there are an increasing number of tools which automate the process and which do not require the user to know a programming language. A number of graphics programs and WYSIWYG editors also incorporate this facility.

Subjects: Computing.

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