Don't Scale Images in HTML
How not Scaling Images in HTML improves Web site download performance
Don't use a bigger image than you need just because you can set the width and height in HTML. If you need <img width="100" height="100" src="mycat.jpg" alt="My Cat" /> then your image (mycat.jpg) should be 100x100px rather than a scaled down 500x500px image.
Other Topics
Overview Web Site performance Improvement Minimize HTTP Requests Use a Content Delivery Network Add an Expires or a Cache-Control Header Gzip Components Put Stylesheets at the Top Put Scripts at the Bottom Avoid CSS Expressions Make JavaScript and CSS External Reduce DNS Lookups Minify JavaScript and CSS Avoid Redirects. Remove Duplicate Scripts Configure ETags Make Ajax Cacheable Flush the Buffer Early Use GET for AJAX Requests Post-load Components Preload Components Reduce DOM Elements Split Components Across Domains Minimize the Number of iframes No 404s Reduce Cookie Size Use Cookie-free Domains for Components Minimize DOM Access Develop Smart Event Handlers Choose over @import Avoid Filters Optimize Images Optimize CSS Sprites Don't Scale Images in HTML Make favicon.ico Small and Cacheable Keep Components under 25K Pack Components into a Multipart Document Avoid Empty Image src
