Admin tabs don't display correctly in Webkit browsers
The admin tabs don't display correctly in Webkit browsers (such as Safari and Chrome). This is due to the facts that those browsers don't wait the images to be loaded before doing the script
common/libraries/plugin/jquery/jquery.ui.tabs.paging.js, so the tabs' width is not correct.
A workaround is to put the image in the background using CSS with suitable paddings. The attached patch contains an implementation of this solution.