HTML 4.01 in Netscape and Explorer: Objects, Images and Applets

Objects, Images and Applets
Make it look nice

The img element

The img element is supported as stated in the specification by both browsers, with the exception of the longdesc attribute which is unsupported. However, both browsers support a few extra features of the img element.

The lowsrc attribute supplies an alternate URI for the image, supposedly for lower resolutions, which has the effect of the image indicated by lowsrc to be loaded first, and then the image indicated by src to be loaded and displayed on top. This is a useful technique to use for large images, especially image maps, where a small, grayscale or wireframe version of the image can be loaded initially so the user doesn't have to wait for the full image map. Both browsers support a name attribute to the image which is used to refer to the image in scripts. Netscape also supports the suppress attribute, which accepts a value of true or false, with the default being false. If it is set to true, the "missing-image" icon is not shown while the image is loading, and the value of the alt attribute is not shown when the mouse is passed over an object. The suppress attribute has no effect if loading of images is turned off.

Explorer supports a dynsrc attribute to img that takes a URI value that specifies a video clip or VRML world to be shown instead of an image. The optional loop attribute indicates how many times the file should loop through a video clip inserted in this way.

The object element

The object element has a long and sad history. Although a very early proposal by the W3C, and one of the most reliable way to embed objects in HTML documents to date, it is still only spottily supported. Netscape graciously displays the contents of the element when it cannot display the object itself, while Explorer will not display the contents at all. Both browsers refuse to display images embedded using object. Netscape does a relatively good job of displaying video clips embedded using object, as long as implicit height and width attributes are defined (otherwise it makes up its own mind about how large the element should be, and gets it wrong, effectively "clipping" the object to a smaller size). Explorer might display a video clip, if you're lucky, but it will most likely crash instead. Netscape does not support the embedding of other HTML documents using object, though Explorer does, as long as you specify explicit height and width. Netscape will not run Java Applets embedded using object, and Explorer only does so as long as you use a code attribute instead of the classid attribute. Explorer displays ActiveX controls using the object element, as this has been the syntax since ActiveX was first invented.

The applet element

The applet element is supported as stated in the specification by both browsers, except for the object attribute, which is ignored by both browsers. Explorer also fails to recognize the archive attribute.

The param element

The param element can only have a name and value attribute in both browsers, and is used to provide parameters to Java Applets. The type and valuetype attributes as well as their functionality is not supported by Netscape or Explorer.

Image Maps

Image maps are fully supported by both Netscape and Explorer, with the exception of the default value for the shape attribute to the area element, which is unsupported. Explorer intelligently renders the value of a title attribute on an area element as a tooltip when the mouse passes over the specified area in an imagemap, and this is a very useful feature. On a related note, the alt attribute to area should always be set. Although Netscape and Explorer ignore it, Lynx, by far the most popular text-based browser around, can display client-side image maps as menus of the various area elements for users to pick from.