I have never experienced any problem with normal Web activity, such as coming here.
I would hope not.
The day that someone experiences a problem caused by visiting the forum is the day that something drastically wrong has happened - particularly because the forum is hosted on a server running Linux, so a Windows virus /worm wouldn't actually be able to compromise a Linux server environment.
Now, if we were to allow members to upload files with extentions that can often mask viruses/worms (.exe, .pif, .eml, .doc, .vbe, .vbs, .bat, .bas, .bin, .sys, etc), and a member was to upload such a file, whether intentionally or not, problems could result on the PCs of people who might download and execute/open them. But thanfully the forum's system gives us complete control over the types of files that can be uploaded as attachments - we're certainly not about to allow such extentions - and frankly, I can't even foresee any reason why files with such extentions should even be uploaded here...