Things That Will Change -- Images & Tables
Part I -- Overview
Based on the fact that HTML 4.0 is designed to push HTML back towards the pure SGML philosophy of marking up a document for meaning instead of for appearance, it should come as no surprise that images and tables are going to change. The changes to the way images and tables are treated in HTML 4.0 are not as substantial as they will be in future versions of HTML, but considering all the other changes in HTML 4.0, and considering that, fundamentally, images and tables are markup that is only intended to affect the appearance of a document, HTML authors should expect them to change pretty radically in future versions of HTML.
The main changes in images and tables which have been introduced in HTML 4.0 primarily address media compatibility. A person who is using a text-only browser, or a browser which does not have a visual display, such as a text-to-speech synthesizer, or a braille display, obviously is not going to be able to view images at all, and tables formatted to comply with HTML 3.2 will display very strangely, if at all on such devices. Of course, there is no way to make a non-graphical browser display graphics, but the alt attribute for image tags, which allows text-only browsers to display alternate text in the place of a graphical image, is now required.
The changes in the way tables are constructed are pretty substantial, although simple tables remain very similar to the way they were treated in HTML 3.2 and only change radically when they are being specifically designed for display on a non-graphical or text-only browser. In general, tables formatted to be compliant with HTML 3.2 should be compliant with HTML 4.0 as well, but if you know that your target audience will be using non-graphical or text-only browsers, there are ways which tables can be specified in HTML 4.0 which will make the way they are displayed in such browsers much more logical and less confusing. Columns and rows can be grouped so that they all load and display at the same time; groups of information can be identified so that they can be re-displayed without having to refresh the entire table; long tables can be assigned header and footer information between which a table can scroll; and elements have been added which will allow text-only browsers to align columns on certain characters, such as in columns of numbers aligned to a decimal point.