Strange horizontal whitespace on iPhone 4 Safari

Question

While testing my website's mobile version on several devices, I noticed a very strange behaviour.

I have a scrollable content div with overflow: auto, and this works properly on all tested devices, except iPhone 4 on Safari. Other browsers and devices display it correctly, even iPhone 5 Safari.

On iPhone 4 Safari, when you scroll to the end of the content, a lot of extra whitespace appears at the bottom (looks like 100-200% extra height) and the text disappears when scrolling. This doesn't happen on any other devices in Safari, nor does it happen in other browsers on iPhone 4.

Has anyone ever heard of such a phenomenon before? I have absolutely no clue what causes this behaviour or how to fix it.

Since I only have access to a limited amount of devices for testing, I may be overlooking other devices/browsers where this issue also occurs. If you have a mobile device and want to test it as well, the live site is here: Live site. On the mobile homepage, click one of the logo's to expand the content, then try scrolling down. Please post your results in a comment.

• How it looks on iPhone 5 Safari when scrolled down (no issue): Image
• How it looks on iPhone 4 Safari when scrolled down (issue): Image

Answer 1

I would venture to guess that you are exposing a layout quirk in Mobile Safari because of the way that you are hiding/showing the contents of each .company element. Each time that you change the display property of an element, the browser must perform a reflow. Reflows (also called layouts) are prohibitively expense on lower powered mobile devices. This would likely explain why you are only seeing the issue on an iPhone 4.

I myself tested on an iPhone 4 and iPhone 3GS, both running iOS 6.1.3, and I was able to reproduce the issue only when I expanded the top or bottom .company elements, but not the middle one. Perhaps this is because the middle .company element contains the fewer children, meaning fewer layout calculations are needed.

Instead of applying display: block; and display: none; to each of the children in the .company element, I would strongly recommend you simplify your javascript to instead toggle the display property on a single container element. By doing this, you force the browser to perform a reflow calculation only once, rather than for each element that you are individually changing the display property.

P.S.: The "other" browsers on an iPhone (i.e. Chrome and Opera) use UIWebviews. UIWebviews use a modified version of the Nitro Javascript engine (the Safari version has JIT compilation enabled). This subtle difference might explain why the issue can only be reproduced in Safari.