1. A computer program product, comprising: a computer readable storage medium to store a computer readable program, wherein the computer readable program, when executed on a computer, causes the computer to perform operations for customizing behavior of a JavaScript widget on a web page via Cascading Style Sheet (CSS), the operations comprising: creating a HyperText Markup Language (HTML) Document Object Model (DOM) element; assigning a CSS class from the presentation definition language to the DOM element; obtaining a computed style for the DOM element, wherein the computed style is computed based on the CSS class assigned to the DOM element; extracting a styling property from the computed style; parsing the styling property to determine an option to be applied to the widget; and applying the option to the widget.