This research suggests that without feedback, the length of time that users will wait for web pages to load is from 8 to 12 seconds. Nielsen recommends the average of 10 seconds. Bickford, Bouch, and Shneiderman found that most users will bail out of your page at around 8 to 8.6 seconds. Without feedback, that is the limit of people's ability to keep their attention focused while waiting.
If you provide continuous feedback through percent-done indicators, users will tolerate longer delays, up to 20 to 39 seconds, although their tolerance decreases with experience. Users will be more forgiving if you manage their delay experience with performance information. They will also tolerate increased delays if they perceive the task to be computationally complex, like a database access. Try to minimize response time variability by keeping page response times uniform to maximize attunability .
This research suggests the following web page design guidelines:
Load in under 8.6 seconds (non-incremental display).
Decrease these load times by 0.5 to 1.5 seconds for dynamic transactions.
Minimize the number of steps needed to accomplish tasks to avoid cumulative frustration from exceeding user time budgets .
Load in under 20 to 30 seconds (incremental display) with useful content within 2 seconds.
Provide performance information and linear feedback.
Equalize page download times to minimize delay variability.
Web designers exceed these limits at their peril. Users associate slow-loading pages with inferior quality products and services, compromised security, and low credibility. Lower user satisfaction can lead to abandoned web sites and shopping carts.