First, take another look at our <SPAN> definition from the previous section of the column:

<SPAN ID="banner" STYLE="position: absolute;"></SPAN>

The ID attribute is similar to the NAME attribute in that it defines the HTML element's individual name. The ID attribute is used to reference the element in JavaScript. In Navigator, document.banner reflects the element, while document.all.banner, or simply banner, represents it in Internet Explorer.

By now, you probably understand why we introduced browser detection in the first section of this column. Microsoft and Netscape agree on CSS, but disagree on the object model. Navigator treats a positioned element as a new browser window, so you can write to its document object, whereas Internet Explorer features a property that reflects the element's inner content (innerHTML). The following function sets the content of a specific element:

function display(id, str) {
  if (NS4) {
    with (document[id].document) {
      open();
      write(str);
      close();
    }
  } else {
    document.all[id].innerHTML = str;
  }
}

In order to rotate our banner, we'll invoke this function in the following way:

display("banner", "new code here");