document.getElementByIdmethod is very useful but isn't supported in early browsers. To define the method for use in those older browsers, just add this snippet to the beginning of your scripts.
Simply click inside the window below, use your cursor to highlight the script, and copy (type Control-c or Apple-c) the script into a new file in your text editor (such as Note Pad or Simple Text) and save (Control-s or Command-s). The script is yours!!!