Guidelines forWeb Usage
Image Compression
All images for the web should be compressed to a resolution of 96 dots per inch (dpi) to speed download times.
JPEG compression should be used for photographs and continuous tone images. A compression rate of 40% - 60% (or 4 to 6) usually produces the best balance between file size and image quality.
GIF compression should be used for diagrams and line art. Reducing the number of colors may help reduce file size.
Alternative Text
Provide alternate text equivalents for all images using the alt attribute in HTML. Alternate text should convey the purpose or meaning of the image. Including text such as "photo of" or "image of" is not necessary. Alternate text for purely decorative images can be empty or null.
