Page response times

Our work at Ideal Interface leads us to speak with many different clients who want a leading ecommerce website. So whilst specifying this solution we try to define the functional requirements (such as what interactivity the page needs to provide) along with the non-functional requirements... such as what the page download / response times should be.

Now... in my experience this actually takes some explaining to define what you actually mean and how you going to measure it before you are likely to get agreement from the client.

Firstly, its important to understand that all things on the Internet are definitely not equal. Connection speeds (bandwidth), latency, the browser you are using and the speed of your device all contribute to the differences between one user's experience and another.

Q: So, what is an acceptable page download time?

A: This depends on who you ask

For a long time I have used the words of Jakob Neilson, the web's foremost usability expert, who has tackled this subject several years ago. He gives the timescale for user attention between 1 and 10 seconds, after that user flow is broken and users tend to leave the site:
http://www.useit.com/alertbox/timeframes.html

More recently, two seconds has been given by Akamai as the new average of an online shopper’s expectation for a web page to load:
http://www.businesswire.com/portal/site/google/?ndmViewId=news_view&newsId=20090914005141&newsLang=en
(I guess you would expect this from a company who provide fast Internet delivery services!)

However, there is no doubt in my mind that a user's expectation of page download times is gradually increasing. So just because bandwidth speeds are increasing, there is no reason for site owners to increase page size accordingly (or to provide complex or badly-written client-side code that takes ages to render in the browser).