Transparent gifs have a number of uses, the most common of which is to stand against a background graphic without totally abscuring it.They're also handy as part of an animation. If you look round the web you come across transparent gives which have a halo around them. Here's how to avoid that effect.

1. To get a transparent gif you use a piece of software (I use GIF Constructor Set®) to set one of the colours in the GIF to transparent. You can select any of the colours available in the palette supported by that particular GIF.

2. Let's suggest your graphic is predominantly blue against a white background. What happens when the image is created the colours dither to white at the edge of the blue leaving a number of pixels around the graphic in a range between blue and white. When white is set to transparent the pixels which are a shade off white are ignored. When the graphic is shown against anything other than a white background a halo appears around the graphic.

3. To avoid this prepare the graphic against the same colour background you have decided for your page, and then set that colour to transparent. This way the image dithers to that colour, and the halo won't show once the graphic is in situ.

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