Followed this tutorial http://www.sitepoint.com/article/accessible-menu-tabs to duplicate rounded corner tabs on a site I'm working on but the problem is that the first time you browse to the site and hover over a tab there is a flicker of square corners before it caches the two round corner images I'm using. Once it caches the image everything is fine, but it's bugging me that for a second when you hover over the first tab it does this. It does it in the example from the tutorial also if you view the tab they've built in action. Watch the corners closely you'll see them square then switch to round after the browser caches the images.
Is there a way to stop this or is it just the nature of the beast with this method?