If a web-site is secure how safe is it to enter personal information such as social security numbers?

First off, as far as the web site goes, you are probably safe. as far as your personal computer goes, that depends. Do you have a good anti-virus? If not I use AVG Free and as the name implies, it is free. The next option to tackle is spyware. If you have a clean computer Windows Defender, available from Microsoft, works fine. Since we don't know about your computer, I suggest and have use Spybot for many years now both to protect and clean my computers and client computers. A last tool to look at for protecting you form threats is a tool called ThreatFire. This covers the stuff not covered by most traditional AVs like AVG or Norton like root kits. All of these are free and I have included links to these tools. Once you have them downloaded and installed, let them update and then run a scan with at least Spybot and AVG. Good luck on the exam.

Always make sure you see the "s" after the HTTP (https). This tells you the company is using SSL (secure Socket Layer) Technology. That is 128 bit encryption in most cases.

The other question is, "is the company you are submitting the information to reputable?"

If the company is bogus and is using SSL your information is still at risk just not by hackers but by the company itself.

The common mindset is that any large site like ebay, youtube amazon or any of those sites are secure. In reality they are not.

In terms of how secure it is for each site. That is very hard to determine or explain, in your case no one is probably going to be seeing your SS, but it is possible.

And as for spyware, We can't answer that, only a virus scanner on your computer can.

The padlock may indicate secure transmission of data from the website to somewhere else, ie. it is encrypted in transit, but if your computer is already compromised, maybe with a keylogger that records what you type, or the computer used by the recipient is compromised, it is worthless.

Security is relative.

Comodo.com offers a complete suite of security for free it includes a vault for ss# and passwords bank account # yes they can be trusted and its also good for vista for those who want more protection try a external firewall they connect to the machine by a usb or firewire connection

If it is a well known site it should be ok. However, any thing hooked up to the internet can be hacked, so always be careful.