More the DOM elements on the page, slower it renders, slower is the DOM access in JavaScript’s. A high number of DOM elements can be due bad layout design. For instance, nested tables might have been used for layout purposes. Use any HTML Tag where is makes sense semantically. For E.g. DONOT use tables for layouts, but DONOT hesitate to use them where you have to display tabular data, and hence will use reduce DOM elements, in comparison, to a similar structure created using DIVs only..

To test the number of DOM elements in your HTML page, just type the following in the Firebug’s console:document.getElementsByTagName('*').length

There is no set standard as to how many DOM elements are too many. Check other similar pages that have good markup.Eg. Yahoo! Home Page is a pretty busy page and still under 700 elements (HTML tags).