Your servers have less than a second to generate web pages
Lets break it down.
There are 5 stages to displaying a web page
1) Waiting for the website to deal with your "browser click" ( web server queues )
1) Generating the page ( your web server doing its job )
2) Getting the page delivered over the internet
3) DOM processing in the browser ( interpreting the html )
Consumers expect a 3 second or better wait time for the page to be displayed, they may be even more critical on mobile devices. This mainly applies to home pages, product pages and category navigation. Consumers are OK to wait a bit on cart check-out as long as you keep them engaged with some form of loading/progress indicator.
Failure to deliver fast browsing will result in page abandonment. You know yourself that if one internet news source is slow you quickly abandon it for another. There are plenty of articles on the levels of abandonment. Here is one http://blog.kissmetrics.com/loading-time/ - the outtake is that 40% of consumers will abandon a site it the page takes more than 3 seconds. So lets go back to our 5 stages that determine page speed
* Browser - stage 3) and 4) usually takes about a second on first visit ( 80% of pages consumers visit are first time visits for that browser )
* Network - stage 2), can also will take up to second for a rich content page with images on the ever increasingly congested and ISP overloaded Australian internet
* That means that the server processing ( stage 1 and 2 ) need to be finished within a second. Are your servers up to that task, do you even know how fast your page load time stages are?
All websites should run page-speed analytics. Tools like newrelic.com are fantastic at finding problem pages. Start with "google page speed" that will also give you opportunities to improve stages 2,3 and 4. There are many other techniques that also help, ajax, lazy-loading, auto paginate all have a place in well designed sites.
When the question at google was asked - "how fast should it take to display search results" some smart *** kid said "before you have even finished the question", now we all have to live with the page speed bar performance being raised to dizzying heights and must find the funds for faster servers and optimised code.