Issue link: https://read.uberflip.com/i/1146286
140 | Index B beacons, 82 AOL, 113 warning, 83 BrowserMatch directive, 34 browsers, when they act differently, 44 C cache, DNS, 66 cache, empty versus primed, 56 Cacheable External JS and CSS (example), 58 Cache-Control header, 23, 35 max-age directive, 23 top 10 U.S. web sites, 24 CDN (example), 20 CDN (see content delivery network) client-side image maps, 11 CNAMEs (DNS aliases), 47, 81 CNN CSS sprites, 115 percentage of time downloading, 4 performance recommendations, 114–115 text as image, 115 (see also top 10 U.S. web sites) CoDeeN, 20 Combined Scripts (example), 16 component web servers, proximity to users, 18 components delayed, 38 ensuring users get latest version, 27 exaggerating response times of, 39 example with changing ETag, 94 far future Expires header, 25–27 how they are cached and validated, 89–91 conditional GET requests, 90 ETags, 91 Expires header, 89 Last-Modified response header, 90 reuse, 57 stylesheets (see stylesheets) unnecessary reloading, 92 ways server determines whether component matches one on origin server, 90 compression deflate (see deflate) edge cases, 34–35 how it works, 29 HTTP, 7 HTTP responses (see gzip) page weight savings, 36 sizes using deflate and gzip, 31 what to compress, 30 conditional GET requests, 3, 7, 8, 90 ETags, 8 If-None-Match headers, 8 content delivery network (CDN), 18–21 Akamai Technologies, Inc., 19 benefits, 20 CoDeeN, 20 CoralCDN, 20 defined, 19 drawbacks, 20 Globule, 20 Limelight Networks, Inc., 19 Mirror Image Internet, Inc., 19 response time improvements, 20 SAVVIS Inc., 19 service providers, 19 free, 20 top 10 U.S. web sites, 19 Speedera Networks, 19 content, geographically dispersed, 18 CoralCDN, 20 Crockford, Douglas, 70 CSS, 55–62 combined, 15–16 dynamic inlining, 60–62 examples CSS at the Bottom, 39 CSS at the Top, 41 CSS at the Top Using @import, 41 CSS Flash of Unstyled Content, 43 CSS Sprites, 13 Expression Counter, 52 expressions, 51–54 event handlers, 53 one-time expressions, 52 techniques for avoiding problems, 52 updating, 52 what makes them bad for performance, 51 home pages, 58 inline versus external, 55–58 component reuse, 57 empty cache versus primed cache, 56 inline examples, 55 page views, 56 tradeoffs, 58 minifying, 75 post-onload download, 59