3. The method of claim 1 , wherein the saving comprises at least one of: saving, for each DOM element in the saved DOM tree, a first CSS property to be applied to the DOM element and a definition location of the first CSS property, and acquiring, for each DOM element in the saved DOM tree, a value used as an initial value, if the first CSS property to be applied to the DOM element is undefined; and the emulating comprises at least one of: acquiring, for each DOM element in the acquired DOM tree, a second CSS property to be applied to the DOM element and a definition location of the second CSS property, and acquiring, for each DOM element in the acquired DOM tree, a value that is used as an initial value, if the second CSS property to be applied to the DOM element is undefined.
3. The method of claim 1 , wherein the saving comprises at least one of: saving, for each DOM element in the saved DOM tree, a first CSS property to be applied to the DOM element and a definition location of the first CSS property, and acquiring, for each DOM element in the saved DOM tree, a value used as an initial value, if the first CSS property to be applied to the DOM element is undefined; and the emulating comprises at least one of: acquiring, for each DOM element in the acquired DOM tree, a second CSS property to be applied to the DOM element and a definition location of the second CSS property, and acquiring, for each DOM element in the acquired DOM tree, a value that is used as an initial value, if the second CSS property to be applied to the DOM element is undefined. 4. The method of claim 3 , wherein the outputting further comprises displaying the saved DOM tree, in which DOM elements that differ between the displayed DOM tree and the acquired DOM tree are highlighted.