Dreamweaver provides several kinds of visual guides to help you design documents and predict (approximately) how they will appear in browsers. You can do any of the following:
Instantly snap the Document window to a desired window size to see how the elements fit on the page. (See Resizing the Document window.)
Use a tracing image as the page background to help you duplicate a design created in an illustration or image-editing application such as Macromedia Fireworks. (See Using a tracing image.)
Grid marks on the page help you align layers, and when snapping is enabled, layers automatically snap to the closest grid point when moved or resized. (Other objects, such as images and paragraphs, do not snap to the grid.) Snapping works regardless of whether the grid is visible.