Graphics for the Web - Tools/Techniques
Always Use width and height in the img Element
The width and height attributes are not required, but to make your pages load quickly and the way you want, you should always use them.
Always Use the <img /> alt Attribute
Make sure your images are accessible and your XHTML valid with this simple attribute.
Always Set the Image Width and Height to the Real Image Size
Using the browser to resize your images is wasteful and can slow your page loading enormously.