Elements having special tagnames and classes are recognized automatically by UI4W as widgets, and constructed on load time by the library. The following is the correspondence between elements, css classes and widgets.
| Tag name | CSS class | Widget |
| div | uislider | UI.Slider |
| div | uitable | UI.Table |
| form | uiform | UI.Form |
| div | uiwindow | UI.Window |
| div | uiaccordion | UI.Accordion |
| div | uicalendar | UI.Calendar |
| div | uilightbox | UI.LightBox |
For details about special attributtes recognized by each widget when parsing this special html elements, see each widget documentation.