There are issues with using the Forum in Firefox due to Firefox caching the style sheets. To control this follow these steps:
1. In Firefox click Tools > Options > Privacy Tab >
2. Click the option that reads ‘clear now’ or ‘clear your recent history’ (the wording may differ in various versions).
3. When you click this, a dialogue box may appear – on this box is a ‘Details’ option – click to expand this to show a list – and then make sure that the option for ‘Cache’ on the list is checked (ticked). Then select ‘Clear now’.
To avoid doing this regularly, you can tell Firefox not to cache in future:
1. In Firefox click Tools > Options > Privacy Tab >
2. On the ‘Firefox will’ dropdown options, select ‘Never remember history’ then click OK.