I've created a simple page that is located at http://quatorze.atspace.co.uk/Webdev/shared/ffbug4.html Page contains iframe. Clicking the button "HIDE" sets "display" property of iframe to "none" so the iframe disappears. Page loaded in iframe contains two divs. Each div contains a link that reffers to that div. :target pseudoclass is set on each div, that makes a div change its background color when it gets reffered. In order to reproduce this bug please take following steps: 1. Click "DIV 1". Background of first div turns grey; 2. Click button "HIDE". iframe disappears; 3. Click same button "SHOW". This makes the iframe reappear; 4. Now click "DIV 2". Background of second div turns grey but background of first div doesn't return to its initial color (as it happens in Chrome) but remains grey.