Your child sits on the computer sees a meaningless blog post on a cartoon forum. The post contains a link. Your child doesn't really know much, and casually clicks the link. Your child didn't know it was a SPAM link from a nameless person on the other side of the world who cares nothing for cartoons. The screen opens up to a graphic video of a person being killed. A real person being killed, not a hollywood actor. Your child has just been traumatized, in the span of a the time it takes to make toast, there are now images embedded in your child that will never be removed, and cannot be undone. This is a true story, it is not far-fetched, and similar versions of it happens all the time. The same scenario can play out with pornography, or any other wretched type of video or imagery that should never come across the eyes of your child. As adults, this stuff can sicken us as it is, but we have built up resilience and are better able to process it, even though some of it can linger in us as well. A child is still innocent. We all know the argument "well that is the real world!" It sure is. The real world contains a lot of terrible things, and a parent's job is to protect their children from the real world so they can have a time of innocence and growth. "The real world" argument is never an excuse to expose a child to everything that happens in it. A child is not meant to witness the brutal raw reality of full human depravity and those who do need special guidance and love.
Or what about this scenario: your child starts chatting online with a cool new friend his age he met on Facebook. He discovers that they have a lot of similar interests. They start sending each other messages regularly and he shares a lot of information about himself with his new friend: where he goes to school, which awesome house he lives in, when his next soccer match is. Little does he know that he is not actually messaging anther little boy but in fact a child predator, a grown up twisted man, 45 years old posing as a young boy. Oh how many times has this happened...every single day! There are adults who specifically troll children's websites looking for any opportunity to snare a child into a sickened web.
Protecting Your Child From Internet Pornography and Violence
One of the most important ways to protect your child is to regulate their internet access. And this means do not give your child private access to the internet in their bedroom. A computer in a child's bedroom is basically saying "I concede, go ahead and have access to porn and snuff films and chat with strangers, I trust your judgment." Do you really trust your child's judgment? Children are naturally curious about the world. If you give your child private, bedroom access to the internet, you should pretty much just tell yourself that viewing pornography will be a given. 79% of youth unwanted exposure to pornography occurs in the home. Four out of five 16 year-olds regularly access pornography online. 12% of all websites are porn sites.
Nine out of 10 children aged between eight and 16 have viewed pornography on the Internet. In most cases, the sex sites were accessed unintentionally when a child, often in the process of doing homework, used a seemingly innocent sounding word to search for information or pictures. (London School of Economics January 2002).
Ninety percent of 8- to 16-year olds have viewed porn online — and most of those say they had done so when they were supposed to have been working on homework.
Of students aged 13 and 14 from schools across Alberta, Canada, 90 percent of males and 70 percent of females reported accessing sexually explicit media content at least once. (Thompson, Sonya. "Study Shows 1 in 3 Boys Heavy Porn Users". University of Alberta Study, 5 March 2007, http://www.healthnews-stat/com...0&keys=porn-rural-teens.)
Children have increased access to violent and pornographic images and videos with the invent of the internet. Porn sites often trick children into opening a sexually explicit sites by linking their sites with harmless and common internet searches. For example, someone may be doing an online search for dirt bikes or a popular cartoon character and a porn site may “pop-up” once the innocent site is opened. Worse, sometimes porn sites are “mousetrapped” so that when users try to close the site, they are actually directed to another porn site. 34 % of youth who use the internet were subject to unwanted exposure to sexually explicit material while another 13% of youth visit x-rated sites on purpose.  Popular online games are also treasure troves of violent images and sexually explicit scenes.
We recommend that you put the computer in the family room, or restrict IPAD and mobile internet devices for use in common areas, so that your child doesn't have the option of going to questionable websites in a private space.
Now obviously at some point you have to turn things over to your child as they approach 18, as trying to regulate too heavily the internet use of an older child can backfire without a solid parent-child relationship and communication structure in place. But for younger children, some form of internet regulation is the best sure-fire way to protect them.
If you are tech-savvy you can install software on your router, or right in front of your router that will record every website visited. This allows a parent to "monitor" every place their child goes. This wont stop a child from accessing and viewing the content, but at least it will let a parent know where their child has been. There are also programs that block websites, and this can offer a great source of protection, even though those as well aren't perfect. http://www.opendns.com/ is a website that allows parents more control over where their children can access and allows monitoring. Remember that every single internet device in your home accesses the web through the same router. So you can always install hardware and/or software right at the router that will monitor and filter whatever you choose. If you don't know how to do this, you can call a local tech store, like a Best Buy and they can come out and do it for you.
What if my child was already exposed?
If your child has a lot of private access to the internet, there is a good chance exposure has already happened. This is where communication and parent-child relationships are key. Don't let your child create a secret "hidden" world, this will only reinforce a duality within them that will carry onto adulthood. Many teenagers have not just viewed porn, they are addicted to it. Millions of porn consumers are children under 18, who watch it regularly. In the same way a hard drug like crack can create an instant addiction, porn is equally as powerful. The first time a child sees it may be unintentional, but immediately they are hooked, and will want more. If this is done in secret, then your child begins to lose their integrity as they have both an outside and hidden side to themselves. Addictions rob people of so much in life, and you do not want your child to carry an addiction to porn into adulthood. The best way to help a child exposed is to bring it into the light, so that the "secret world" is no more. Find a counselor to help you through it, and establish communication and trust with your child.
Protecting Your Child From Internet Predators
With the internet age, children have amazing new resources to communicate, make friends, gather information, and see the world at the touch of a fingertip. There are wonderful reasons why your child should be an internet user.
However with the virtual exposure to the world comes the increased exposure to world dangers. Children are sharing an exceptional amount of information about themselves online, especially on social networking sites, which makes them more susceptible to crimes such as bullying and child enticement or to having sensitive information about them published. In 82% of online sex crimes against minors, the perpetrator used the child's social networking site to learn about their likes and dislikes and 65% of sex offenders used the child's social networking site to find out their address and school. 43% of teens report that they have experienced cyber bullying in the past year. 20% of teens have posted nude or semi-nude photos or videos of themselves online which immediately puts them at risk of that content being shared, exposing them intense humiliation and ruined reputations. 
Although it would be great if our kids told us everything, don't always count on them to tell you about what they are up to online. It is up to you to keep track of their internet use and behavior. Keep a record of their e-mail addresses, logins, passwords and display names, which are recorded already in your computer files. Learn how to use the social media sites that your child uses and keep up to date with the privacy features of these sites, making sure they have been enacted. Be aware of your child's behavior by “friending” them on Facebook.  They may die of embarrassment, but in this way you can keep track of what information they are sharing and more importantly with whom. It is also your responsibility to become proficient enough with your computer to know how to use filters, parental controls and safety software such as malware removers and anti-viruses.  If you don't know how to do these things, have an older teen show you how. In addition to these safety protocols, put the computer in a common space in the house, especially with young children, rather than in private areas and set up agreed upon family internet rules.
Explain to your child the dangers of the internet.  It is absolutely imperative that they understand that what information they share about themselves online is public, even if it is intended to be private as it can be shared with anyone. Once something is online, it is very difficult to get it removed. Therefore children should never use their real names, post phone numbers or addresses and limit photo sharing. Children should never, ever share nude or explicit photos or videos of themselves or agree to meet a person they do not know.
Encourage your child to tell you if they have been solicited. If they are behaving secretly about their online use, become upset when internet access is denied, start receiving phone calls or packages from someone you do not know, and begin downloading pornography it is fair to suspect that they may be engaging in conversations with a predator. 
The best way to protect your child from the wild world of the internet is to talk to them and encourage communication. They may not want to tell you everything they are doing, (would you have wanted to when you were young?), but if you are actively participating your child's life, perhaps they will feel safe enough to tell you when something has made them uncomfortable online.
 [http://www.internetsafety101.org/snsdangers.htm ]
[“Online Victimization of Youth: Five Years Later” http://www.missingkids.com/en_US/publications/NC167.pdf ]
 [A Parents’ Guide to Social Networking Websites http://www.ag.idaho.gov/publications/internetSafety/ParentsGuideToSocialNetworkingWebsites.pdf ]
 [Internet Safety http://www.atg.wa.gov/InternetSafety/FamiliesAndEducators.aspx#.Uhvq1z-t0lI ]
 [Internet Safety for Teens http://www.education.com/reference/article/Ref_Teens_Internet/ ]