Use image editing software to reduce the dimensions (and also file size) of images rather than setting the dimensions (and not reduction in file size) with the web page authoring software.

Which image is 22 kilobytes, which is 124 kilobytes and which image is 1406 kilobytes ?

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The image above was forced to display 400x300 pixels by the width and height tags in the html code. The dimensions were set with the html authoring software. Using the webpage authoring software to reduce the dimesions of the image does not reduce the file size. This file is 1406 kilobytes.

The two images below had their dimensions reduced by image authoring software. Their file sizes are 22 kilobytes and 123 kilobytes respectively.