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 of todays web pages are made up of a collection of components including CSS files, javascript, images and often movies. For fast page load times it is essential to minimise the number of these elements and therefore the number of HTTP requests that the browser must make in order to render a page.
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. On a first visit a number of HTTP requests are made in order to download these elements. If these are cached then there is less to download on a subsequent visit 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 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.