The internet can be fun and educational. But it can also be dangerous and threatening. Largely unmonitored and uncensored, it is a mixed environment which can be a source of material and intellectual sustenance for you, but it can also bring a lot of annoyance with it, and even cause damage to your near and dear ones.
There are certain safe practices you can adopt to avoid the typical pitfalls that await the careless surfer on the web. First, there is the nuisance of the unwanted pop-up. These can sometimes be of a pornographic nature, causing undue harassment and embarrassment in public situations. In order to suppress these, use a modern browser like the Internet Explorer enhanced with Windows Service Pack 2. An even better choice is the freely downloadable Firefox browser, which you can get from here.
Also beware of spyware programs and other malware that can get installed on your computer without your direct endorsement. A useful strategy is never to click on any window that offers such a service unless it is from a known and trusted source. Also, use one of the freely available spyware removal programs to rid your system of these threats.
Viruses, worms and trojans are rampant on the web; an unprotected Windows system can get infected in a matter of minutes after getting connected to the internet. Install one of the commercial anti-virus solutions from Norton, Macafee or other companies to protect yourself from this kind of threat as far as possible. Very good free anti-virus products are also downloadable from locations on the internet; you can find one such here.
A more radical strategy to beat the threat of viruses and worms would be to opt for an Operating System other than Windows. If you aren't inclined to buy an Apple Macintosh machine, you may consider installing Linux on your existing computer. No real virus has yet been invented for the Linux environment, and it is unlikely that one will appear as a real threat in the near future, because of the excellent inherent security model of that system. You can choose from a number of free Linux systems, and some of the best choices can be found here and here. If you can't do it yourself, you can find a paid support provider who will install and configure it for you.
Use a firewall to rid yourself of unwanted connections to and from your computer. The firewall built into Windows XP is effective, but not configurable. For a more flexible solution, try ZoneAlarm, a feature-limited demo of which can be downloaded here. If you're using Linux or at least using a Linux box as a gateway, you can experience the great power and configurability of its built-in iptables firewall.
Whatever browser you use, it is best not to keep checked any option that will let it download and install programs unsupervised. Many harmful programs get installed in this way.
If you're using Windows, create a non-administrator account for yourself and use that for all normal purposes. This way, any virus or malware that gets in shall have a very hard time getting activated.
Under Windows, most harmful programs use a particular feature in the Internet Explorer browser to get installed. This feature is known as ActiveX. To avoid this weakness, use any of the free non-Microsoft browsers available. Firefox is one, a link to which has been given above. Another very good free browser is Opera, downloadable here.
A new type of online threat is known as phishing. Fake web pages are constructed that look like your bank's website, or that of your stockbroker. You are invited to enter your credit card numbers and other sensitive information, which are then used for illegal purposes. Always double-check the address whenever you are asked to enter any such info. Firefox has an inherent capacity to detect phishing sites.
Never download files from unverified sources that have a dot-exe or a dot-com extension. These are the commonest carriers of viruses and other malware, and can cause a lot of grief if handled by inexperienced hands.