Images

Though images improve the appearance of a website and facilitate the understanding of information, they could reduce the satisfaction of the users if not used properly, causing them to navigate away. When using images, follow the below guidelines:

• Images should only be used if they add value to the content given that images’ quantity affect the downloading time.
• Images must have the same content in “alt” text, as text-only browsers would not access them. They should not be a substitute to present major content (without “alt” text given to it). See section Text Alternatives for Non-Text Content.
  Example:

  A common text-only browser is called Lynx and can be accessed on http://lynx.isc.org
• The use of text (instead of images) should be taken into consideration for headings and navigation.
• Images that are applied more than once, such as those for the government entity’s identity or navigation, should be re-used to reduce the downloading time, since the images will be loaded once, taking advantage of browsers’ caching (e.g. use the same background image file for two different page elements that need this image).
• Anti-aliasing functionality should be avoided whenever feasible while saving an image. Anti-aliasing increases colors to the image, which results in large file sizes.
• Textured or tiled backgrounds should be avoided as they weight down the page and reduce the legibility of text.

Images should be produced in a suitable format to decrease the loading time without jeopardizing the quality. The 3 formats used in web browsers are GIF, JPEG and PNG.

• GIF format is to be used for images that contain flat areas of colors, such as icons buttons or image text.
• JPG format for images that contain multiple colors variation such as for example photographs.
• PNG format for an image that need to display a transparency and show what is below it (for instance, a text image over a background). However, this format is also valid for other usage and does not have to be limited to transparencies; it can be read and written freely by any software.