49Chapter 13 .JavaScript Essentials Older graphical browsers, PDA (Free web space)
49Chapter 13 .JavaScript Essentials Older graphical browsers, PDA browsers, and Lynx. The last category includes graphical browsers some call brain-dead, as well as intentionally stripped down browsers. Lynx is designed to work in a text-only VT-100 terminal screen; personal digital assistants (PDAs) such as the Palm handheld computer have browsers optimized for usage through slow modems and viewing on small screens. If such browsers do not understand the tag for refreshing content, they land at this page with no further automatic processing. But by creating an image that acts as a link, the user will likely click (or tap) on it to continue. The link then leads to the nonscriptable home page. Also note that the ALT attribute for the image is supplied. This takes care of Lynx and PDA browsers (with image loading off) because these browsers show the ALTattribute text in lieu of the image. Users click or tap on the text to navigate to the URL referenced in the link tag. I have a good reason to keep the background of the branching index page plain. For those whose browsers automatically lead them to a content-filled home page, the browser window flashes from a set background color to the browser s default background color before the new home page and its background color appear. By keeping the initial content to only the company logo, less screen flashing and obvious navigation are visible to the user. One link alternate destinations Another filtering technique is available directly from links. With the exceptions of NN2 and IE3, a link can navigate to one destination via a link s onClickevent handler and to another via the HREFattribute if the browser is not scriptable. The trick is to include an extra returnfalsestatement in the onClick event handler. This statement cancels the link action of the HREF attribute. For example, if a nonscriptable browser should go to one version of a page at the click of a link and the scriptable browser should go to another, the link tag is as follows: Product Catalog Only nonscriptable browsers, NN2, and IE3 go to the nonJSCatalog.html page; all others go to the JSCatalog.html page. Multiple-level scripts Each new JavaScript level brings more functionality to the language. You can use the LANGUAGE attribute of the