Will adding rules improve security if I access only a few trusted websites?

The post “Filtering internet – how do I allow only certain websites?” is related to my
questions, but doesn’t completely deal with them. I haven’t found anything else that I
recognize as being part of an answer. I’d greatly appreciate anyone’s thoughts, and thank
you in advance.

I start with a clean system. It’s XP home with SP2. I use CA anti-virus software and anti-
spyware (from my ISP). I keep all the security software, including XP, updated and have
only minimal other software installed.

I want to access only about six websites (which I absolutely trust), in addition to the
update sites for CFP, the CA software and XP.

I don’t ask CFP (2.4) to remember anything. Each startup, I receive a few warnings
similar to: “C:\Program Files\Yahoo\YOP\yop.exe has tried to use ycommon.exe through
OLE Automation, which can be used to hijack other applications. Yop.exe might be using
ycommon.exe to connect to the Internet.” I believe (hope?) that the programs involved
are part of a normal connection to the Internet.

My first question is this: If instead of simply remembering which websites that I want to
allow, would the system be more secure if I composed rules to limit access to only those
websites (Other than to protect me from myself – no small matter :))? Then too, I wonder if
I would receive an alert if malware tried to use ycommon.exe as in the example above?

Again, thanks in advance.