The actual and relative styles and sizes can not be specified but a chosen by the user and the browser. The SGML specifies rules about what is recommended, normal and deprecated. Document Type Definition . The 'alt' attribute is what is shown to a browser that does not show the image - some browsers do not show graphics. The ismap attribute indicates that parts of the graphic are hot buttons that act as links to other pages etc.
Maps take time to construct without some special purpose tools.
Remember that each graphic takes time to transfer over the network. Animated graphics, in particular are resource hogs. The CGI rules define how data is given to a program on the server. The program then runs and generates a page that is returned to the browser, using a standard format. Personally I use UNIX shell scripts.