The simple source of this page shows precisely what is causing the horizontal navigation bar on the Canterbury University website to display broken. The stylesheet on that site containing the problematic rule is common.css (line 447).
By removing the 'first-line' rule from the CSS source - which shouldn't apply to those links anyway because the selector doesn't match - the links below are displayed next to each other as expected.
Note that removing the problematic rule from the stylesheet using the document.styleSheets Javascript object doesn't correct the display until you alter the DOM of the elements showing this problem. In this case, the DIV element containing the links. Even appending a null string to the DIV's innerHTML property is enough to update the display, something which isn't usually required to update the page when editing stylesheets via Javascript.