We all know, instinctively, that most web users don’t have the patience for pages that are slow to load, or won’t load at all. But what does the hard data say?

A WP Engine study concluded that a delay of just one second can lead to 11 percent fewer page views and 7 percent fewer conversions.

Things only get worse as delays get longer. A survey by Gomez.com found that 75 percent of customers left for a competitor’s site due to slow speed during peak traffic times. Even worse, 88 percent of customers said they were less likely to return to a website after one bad experience.

You only have one chance to make a good first impression. But if you aren’t focusing on building a nimble, responsive web page that will be available when people want to visit it, all of your other user experience design decisions lessen in importance.

What are UX designers to do? Here are some things to keep in mind:

• Load test your servers. This should go without saying. If your web page is going to be popular, it needs to stay functional under the weight of a great deal of use. Otherwise, you’re losing business that you should have been able to earn.
• Incorporate conditional loading. Not everything needs to load all at once – just the important things. Conditional loading can break web content into sections and only load them when certain conditions are met. This means that the most important content will always have priority. Users with weak connections who still want to access your product will thank you.
• Avoid misleading progress bars. There’s no point to a progress bar if it remains frozen at 99 percent complete for several minutes. If your design element doesn’t work as intended, it will just frustrate people, and should be scrapped.