What Every Web Developer Should Know About Site Performance
Since Google’s recent announcement that web page load times are now a ranking factor web designers and developers have been required to pay additional attention to site performance considerations. Here are just a handful of factors that todays web developers need to keep in mind.
Most web pages are made up of a collection of elements including javascript files, CSS, images and database delivered content. Minimising the number of elements and therefore the number of HTTP requests necessary to render a page is crucial for fast page load times.
Around 80% of the end user’s response time is consumed in waiting for all of the page elements to download. It is well known that this waiting time can prompt visitors to leave an ecommerce site and visit a faster loading competitor. Using a content delivery network to serve the static content, including javascript and CSS files, can significantly reduce this time. A content delivery network is simply a collection of servers setup to efficiently deliver content to end users.
As web designs become richer and more engaging to the end user they require an increasing number of components including javascript, images and maybe Flash. When a site is first visited a number of HTTP requests will be made to download all of these elements. These can be minimised on subsequent visits by caching and this can be controlled using the Expires header. This is commonly used for images but can be effectively used for all components including Flash and stylesheets.
Compression, perhaps using GZIP, is another technique that should be in every web developers speed optimisation arsenal. GZIP is supported by around 90% of todays browsers and it can reduce the size of many elements by as much as 70%.
There are many additional techniques that can aid not only the search engine optimisation of web pages and will also improve the user experience. These include putting stylesheets at the top of pages and scripts at the bottom; minifying both javascript and CSS files; putting javascript and CSS into external files; reducing the number of DNS lookups and avoiding redirects. Good luck.
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