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Use shorthand properties in CSS to shrink your style sheets. 
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The cost of banner ads for the average website is about one-sixth more objects and one-third more latency. Learn how online advertising affects web page response times, user behavior, and satisfaction.
Mickael Ruau's insight:
To capture the limited attention spans of visitors, advertisers have increased the size of their ads. Larger ads, on the order of 360x240 pixels, have been shown to have significantly higher clickthrough rates than do the smaller ads of 468x60 pixels (Robinson, Wysocka, and Hand 2007). Advertisers have resorted to pop-up and pop-under ads to deliver their message, but these have been shown to annoy users and reduce their intention to return (McCoy et al. 2007). The number of ads for the average web page has also increased over time with the average popular page containing over 8 ads. Sponsored advertising has increased, with more than twice the share of ads for paid search as opposed to banner ads, according to projections (Laffey 2007). Off-search PPC ads appear as graphic text ads, adding to the profusion of banner ads. All of these trends mean an increase in the file size and in the number of banner ads for the average web page. This article examines the effect of banner ads on web performance. What price do we pay for banner ads on the Web?
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With the average web page growing past 50 external objects, object overhead now dominates most web page delays. Increasing parallel downloads by using multiple hostnames can realize up to a 40% improvement in web page latency.
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Website optimization speeds up slow web sites, increases website traffic, and improves conversion rates. Our web optimization services increase website performance, decrease bailout rates, and improve search engine rankings.
Mickael Ruau's insight:
Un site web dédié à l'optimisation web.
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Optimisation du code JavaScript, du poids des pages, des requêtes-réponses... La conférence Velocity Europe d'O'Reilly a fait la part belle aux enjeux de performance Web.
Mickael Ruau's insight:
Dans sa présentation, Chris Heilmann, de la fondation Mozilla, a notamment insisté sur l'importance d'éviter la fonction JavaScript eval(), qui permet de créer du code dynamiquement (avec en arguments la possibilité d'ajouter des variables et des objets). Problème : elle empêche la mise en cache du code en question, ce qui peut engendrer des baisses de performance. Autres conseils : favoriser le code JavaScript avec un typage stable, et éviter de créer des objets sur des boucles.
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HTML CodeSniffer est un script exécuté à partir d'un bookmarklet permettant d'établir un rapport concernant la conformité de votre code HTML avec les standards d'accessibilité définis par le W3C: les fameux WCAG 2.0.
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Round-up of 10 easy-to-follow performance boosters for jQuery. Optimize selectors, use better functions and learn other jQuery performance secrets.
Mickael Ruau's insight:
Before Paul’s talk my understanding of jQuery performance tuning was fairly simplistic: Optimize selectors to descend from an id if possible.Use tag names when selecting classes and don’t use an excessive number of selectors.Define variables instead of selecting the same object repeatedly.Optimize your code replacing repetition with object oriented functions.But the information Paul presented blew all that out of the water. Here are 10 jQuery performance rules I gathered from his presentatio
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a blend of web development, science, education, and coffee
Mickael Ruau's insight:
Still, I was surprised how little information I found on the subject. A quick google search turns up a few great resources. To mention a few: An overview of Nicholas Zakas’s tips, Google’s “Make the Web Faster” article, and An older article by Jeff Greenberg.
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In computer science, Duff's device is an optimized implementation of a serial copy that uses a technique widely applied in assembly language for loop unwinding. Its discovery is credited to Tom Duff in November 1983, who at the time was working for Lucasfilm. It is perhaps the most dramatic use of case label fall-through in the C programming language to date. Duff does not claim credit for discovering the concept of loop unrolling, just this particular expression of it in C. Loop unrolling revolves around lowering the number of branches made, by batching them together. To handle cases where the number of iterations is not divisible by the unrolled-loop increments, a common technique is to jump directly into the middle of the unrolled loop for copying the remainder. Duff was looking for a similar optimization for his case, and succeeded in doing so in C, unrolling a loop into a loop which assigns (up to) 8 values on each iteration.
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Just another script compressor, and that's by far the easiest to use! Use Jasc to merge compress your javascript (JS) and style sheets (CSS). Jasc is meant to be simple yet effective: just drop the executable in your javascript / CSS folder and run it. Voyla! It will handle everything by itself.
Mickael Ruau's insight:
Compression is based on Microsoft Ajax Minifier. Jasc can handle single or multiple files, will accept regular expressions to remove specific lines from the source code, and can also optimize the results by shrinking variable names and tweaking the source code. Compiled in Mono C# 3.0, runs on Windows, Mac and Linux.
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Compression, gestion des délais d'expiration, du cache... Le serveur web peut subir un traitement de choc qui permettra d’améliorer grandement le temps de chargement des pages. Tour d'horizon.
Mickael Ruau's insight:
Le constat est sans appel : en moyenne 45% de temps de chargement gagné pour chaque page. Bien entendu, de nombreuses autres possibilités d’optimisation existent, notamment avec l’usage des Content Delivery Network, mais là, nous entrons dans le monde des experts et dépassons le cadre de cet article. De la même manière, si vous possédez votre propre infrastructure, différentes alternatives s’offrent à vous en termes de compression, routage et gestion de flux. Quoiqu’il en soit, en matière d’optimisation, il faut toujours commencer à la source ! Maintenant, c'est à vous, car n'oublions pas qu'il est communément admis qu'à chaque seconde de chargement d'une page, c'est 10 internautes qui fuient !
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Optimisation du nombre de requêtes, utilisation de sprites... Le traitement d'images peut être avantageusement complété par des pratiques pertinentes concernant l’intégration HTML.
Mickael Ruau's insight:
Dans cette partie, nous n’allons pas chercher à optimiser le poids des images, mais plutôt à rendre le comportement du site plus véloce et augmenter sa réactivité. Les bonnes pratiques nous recommandent de toujours spécifier les attributs height et width, ainsi que, si nécessaire, hspace et vspace (à défaut d’une gestion CSS avec margin et padding) pour les balises <IMG>. Ici, l’objectif est, d’une part de faciliter le travail du navigateur en lui donnant le maximum d’instructions exploitables et, d’autre part, éviter les phénomènes dits de reflow qui provoquent un re-calcul de l’affichage de la page.
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GTmetrix, Google PageSpeed Insights ou encore YSlow, plusieurs outils en ligne gratuits existent pour évaluer la performance de chargement et d'exécution d'un site Web.
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By grouping CSS selectors that share the same declaration and declarations that share the same selector you can apply multiple declarations to multiple selectors to optimize your style sheets.
Mickael Ruau's insight:
By combining the grouping of selectors that share the same declaration and declarations that share the same selector you can apply multiple declarations to multiple selectors. This technique allows you to create compact yet powerful CSS rules. This tip combines Group Selectors with Group Declarations into one powerful technique.
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By combining external files and embedding CSS and JavaScript within your HTML you can minimize the number of HTTP requests required to render your page. Each unique HTTP request requires a round trip to a server, introducing indeterminate delays.
Mickael Ruau's insight:
By combining external files and optionally including CSS and JavaScript directly within your XHTML pages, you can minimize the number of HTTP requests required to render your page.
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HCI guidelines say load useful content within 1-2 seconds, do your pages measure up? Learn how to optimize the start render time of your web pages to speed up useful content display.
Mickael Ruau's insight:
The average web page has grown inexorably as bandwidth has increased. The average web page has over 100 objects and is 1200K in size (HTTPArchive.org). Many of these objects are loaded in the HEAD of (X)HTML documents (external JavaScripts being the main culprit), contributing to slower start render times. In performance audits we've seen start renders in the 5-6 second range in some cases, even on cable modem connections! In light of this distressing situation we find ourselves in, this article shows how to speed up your start render times with some best practice methods. Before the web page starts to render, browsers must download and parse the objects on the HEAD element, and calculate the initial layout before content can show up on the screen. Optimizing your start render time is mainly a function of server response and optimizng the efficiency of the elements in the HEAD of your HTML documents. There are a number of best practives that can be used to speed up start rendering.
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Excerpts from the New Riders title, Speed Up Your Site: Web Site Optimization.
Mickael Ruau's insight:
Book excerptsChapter 2: Flow in Web DesignChapter 9: Optimizing JavaScript for Download SpeedChapter 10: Optimizing JavaScript for Execution Speed
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Récemment, j'ai pas mal bouquiné dans un tas de livres et d'ebooks traitant de javascript et certains points qui étaient un peu flous pour moi sont devenus plus clairs.
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a blend of web development, science, education, and coffee
Mickael Ruau's insight:
A while ago I posted about Proportional Resizing of Web Page Elements Using Only CSS. At the time, it seemed like the only solution… but fortunately a slightly counter intuitive CSS standard provides a much better way to get this same effect. Credit goes to Nathan D. Ryan for his solution on Stackoverflow.
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Javascript optimization isn't black-and-white, but here's 10 Javascript Performance Tips from Nicholas Zakas that will make your Javascript fly.
Mickael Ruau's insight:
This article is part of the series 10 Javascript Performance Tips, which takes the advice of industry leaders and boils it down into ten easy-to-follow guidelines. Check out 10 Advanced jQuery Performance Tips from Paul Irish and stay tuned for more.
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I just finished reading "High Performance Javascript" and wanted to file this little bit of optimization away for a time of need. There's a brief discussion on page 66 on using Duff's Deviceto eliminate numbers of loop runs.
Mickael Ruau's insight:
//credit: Jeff Greenberg var iterations = Math.floor(items.length/8), startAt = items.length %8 i = 0; do { switch(startAt){ case 0: process(items[i++]); case 7: process(items[i++]); case 6: process(items[i++]); case 5: process(items[i++]); case 4: process(items[i++]); case 3: process(items[i++]); case 2: process(items[i++]); case 1: process(items[i++]); } startAt = 0; } while (--iterations);
They provide a second implementation: var i = items.length % 8 while(i){ process(items[i--]); } i = Math.floor(items.length / 8); while(i){ process(items[i--]); process(items[i--]); process(items[i--]); process(items[i--]); process(items[i--]); process(items[i--]); process(items[i--]); process(items[i--]); }removing the switch statement. The author then discusses when to use Duff's Device in Javascript: In cases where the loop iterations are less than 1000, you're likely to see only an insignificant amount of performance improvement over using a regular loop construct. As the number increases past 1000...the efficacy of Duff's Device increases significantly. At 500,000 iterations...the execution time is up to 70% less. Pretty slick.
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Comprehensive PHP Benchmark tests (PHP Bench).
Mickael Ruau's insight:
Use foreach unless the hash is lage AND has lage data elements. In that case use variation Nr.3 .
(...) Using the &-ref-operator as so called "alias"Is a good idea to use the &-ref-operator to substitute (or alias) a complex mutidim-array? . Call 1'000x Conclusion: (...) Always calculate the length of the loop in advance! (...) Using a switch/case or if/elseif is almost the same. Note that the test is unsing === and is slitly faster then using ==.
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De la compression du code HTML à la normalisation des CSS, voici quelques bonnes pratiques indispensables pour réduire le poids des pages web, et améliorer leur vitesse de chargement et d'exécution par les navigateurs.
Mickael Ruau's insight:
Si votre site utilise des affichages évolués, ou que vous souhaitez une maîtrise "absolue" de l’affichage, la normalisation CSS semble alors plus appropriée que les techniques de reset CSS. Vous pouvez par exemple utiliser normalize.css qui pallie, de manière optimisée, les écarts entre navigateurs. Un autre aspect apparemment anodin concerne la page HTML codée, dans laquelle un développeur sérieux va placer des indentations, retours de lignes et commentaires. Par exemple, une indentation peut-être réalisée avec une tabulation (1 octet) ou 4 espaces consécutifs (4 octets). L’écart unitaire de 3 octets peut sembler insignifiant, mais qu’en est-il sur une page de plusieurs centaines de lignes ? Ajoutons à cela les espaces laissés en fin de ligne, la surabondance de sauts de lignes utilisés pour aérer le code et les nombreux commentaires… Nous pouvons ainsi facilement récupérer des centaines, voire plusieurs kilos octets sur une page, sans aucune conséquence négative pour l’internaute ni perte de la lisibilité nécessaire à la maintenance.
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Pour réduire le poids des codes JavaScript et CSS, la meilleure démarche est d’utiliser des minimiseurs. Autres leviers : vectoriser les descriptions de style, et supprimez les descriptions non utilisées.
Mickael Ruau's insight:
nous avons vu dans l’article Optimiser l’utilisation des images d’une page webcomment améliorer la performance du poste le plus gourmand en ressources inutiles, les images, avec la prétention de réduire, parfois, de plus de 75% le volume global. Dans cet article, nous revenons à l’objectif premier : réduire le poids global de votre site, avec un focus sur l’optimisation du poids des fichiers JavaScript et CSS.
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La première cause de lenteur d'un site web est liée au volume de données chargées. Dans ce registre, le poste le plus gourmand concerne, sans aucun doute possible, les images.
Mickael Ruau's insight:
Comme nous l’avons vu dans l’article Pourquoi optimiser un site web ?, améliorer la vitesse de chargement des pages d’un site à au moins 4 impacts directs : le nombre de visiteurs, et par effet de levier le référencement, un gain économique et un impact environnemental réel.
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Shorthand properties allow you to specify a set of related CSS properties with a single property. They combine related properties into a shorthand form. In most cases, the browser sets a default value if you leave out an optional one. There are six shorthand properties in CSS:
fontbackgroundmarginborderpaddinglist