Recommendations

PageSpeed
YSlow

YSlow: Do not scale images in HTML

Overview

Scaling images in HTML can result in unnecessary bandwidth wasted downloading large images.

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Details from Yahoo!

Web page designers sometimes set image dimensions by using the width and height attributes of the HTML image element. Avoid doing this since it can result in images being larger than needed.

Summary

Images
Low
Moderate

YSlow recommends:

For example, if your page requires image myimg.jpg which has dimensions 240x720 but displays it with dimensions 120x360 using the width and height attributes, then the browser will download an image that is larger than necessary.

Resize your images in an image editor to the actual size you need.

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