What Every Web Developer Needs To Know About Site Performance
With Google’s confirmation that the time taken to load a web page is now a ranking factor web developers and designers have been prompted to sit up and pay renewed attention site performance. Here are just a handful of considerations that today’s responsible 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 increasing complex, richer and more engaging to the end user they need an ever increasing number of components in order to render, such as Flash and javascript. 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 header is commonly used for images but it should be routinely employed for all elements including Flash and javascript files.
Compression, perhaps using GZIP, is another technique that should be in every web developers speed optimisation arsenal. GZIP is one of the most popular compression tools, supported by most browsers, it can reduce the size of many elements by as much as 70%.
There are lots of additional techniques that are both good for 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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