I understand your concerns about a "single User account".
I read your thread; http://www.pclinuxos.com/forum/index.php/topic,73799.0.html
which is great as you are trying to get some feedback as to plugging Browser exploits, as a part of securing your 'User Account'. Personally, I find Firefox is a good and hugely supported Browser, security wise. How far you go is up to you. I use Adblock, with a subscription, I could use NoScript, but to get where I wanna go I generally have to turn it off, ...
Oddly, if we were using Windows I could secure my User Account in a snap.
Linux, having a confidence that there are no threats out there, and you've (Just17) been pushing the envelope pretty hard to get some answers, spread the word about vulnerability of user data in the 'user account' have had generic replies of clear your cache, and cookies, don't visit sites that are known to be a risk, which are good advice, but maybe not enough, ...
Went looking online, ... just a start. http://winhelp2002.mvps.org/hosts.htm
Although I do not use either Linux or a Mac, I often get requests for "How To" on that system, so here are a few resources:
*Block unwanted advertisements with /etc/hosts file on Linux
Basically to secure your User Account you're gonna have to Drop the Rights of Files, Directories, so they can't be Read, or Written to, whilst online is my only suggestion, plus a good HOSTS file, play around with DNS, Set up a Firewall. We don't have 'Resident Protectection' as is provided by AntiVirus software in Linux, as far as I know.
Have you played with NMap ? See who might be peeping at you ? I dunno, ... I'm out of my league this being a Linux OS. Plus I'm done, but will watch with interest, Tinfoil hat firmly placed on my head.