Google’s aim is to provide the best resources to its searchers, and this includes listing websites that are easy and fast to navigate. So when Google spiders your website it takes note of how fast the pages are loading, and will list you better for a nice speedy page-load time.
Image Sizes
It’s important for you to know this if you have a CMS system that allows you to upload images, because you’ll need to ensure you don’t load images straight from camera. They will be massive, and although you’re resizing them on your website, browsers will have to download the whole huge image before displaying it, and this takes time. So before uploading images to your website, ensure you resize them to something sensible, in a graphics program.
Website Build
This is one for your website designers – the way your site is built can make a huge different to page loading speeds. Sites can call information in any number of ways and you’ll need to ensure that your site uses an efficient and organised method of calling data, especially if you have a large site with lots of content.
Monitoring Loading Speed
There are two resources I’d recommend for checking the loading time of your website.
The first is Google’s PageSpeed Insights: http://developers.google.com/speed/pagespeed/insights/
This will tell you how fast your pages are loading, and also provide detailed information on what is causing delays and how to fix this (in most cases).
You should also be tracking the information provided in Webmaster Tools, giving you information on how long it has taken Google to download your site pages over the last few months. You can keep an eye out for spikes and unusual delays.