Some people have trouble accessing one of my sites if they're running ZoneAlarm.
The problem appears to be that ZoneAlarm mangles web pages, so that what you see in your browser is not what the web server transmitted, but the bits of the page that ZoneAlarm thinks you ought to be allowed to see.
When my site's users complain to me about this I suggest they regard ZoneAlarm as malware and uninstall it.
Emails to ZoneAlarm suggesting that they might like to consider fixing this sort of bug elicit no response.