Use the ALT element
Remember to include the ALT element within the <IMG> tag to provide a textual label for the graphic.
Use height and width elements
These attributes are important because they allow the browser to allocate sufficient space for the
image without having to wait for the image to completely download before beginning to display the text on the page.
Also gives the user a chance to see the overall dimensions of the image before deciding to wait for the page to download completely.
Transparent and interlaced GIFs
A "transparent" GIF is an image with a transparent background. Transparency makes the image
appear to float on your web page. GIF editor software that supports
the GIF89a standard will probably provide a way to add transparency.
An interlaced GIF, instead of being transmitted and displayed top-to-bottom like a normal image, is first
displayed at its full size with a very low resolution, then at a higher resolution, until it finally attains a normal appearance.
Avoid animated GIFs
Single pixel GIF trick
The single pixel GIF is a clear GIF one pixel in size. Reference it with the <img> tag, using horizontal and
vertical space attributes to make a clear rectangle of any size to use as a spacer.
If I wanted a pixel GIF 5 pixels wide the HTML would be:
<IMG hspace=5 SRC="pixel.gif">
If I wanted a pixel GIF 5 pixels wide by 2 high, the HTML would be:
<IMG hspace=5 vspace=2 SRC="pixel.gif">