Internet censorship is action that prevents publishing or accessing information on the Internet. Such action is often performed by governments or organizations against information they believe to be sensitive or harmful.
Opinions about Internet censorship are opposing in different levels (from strongly disagree to very pleased). These opinions are dependent on the knowledge of a person as well as the censorship laws which varies on country-to-country basics.
Method of applying censorship
User report and request for removal: This action can be done by anyone who thinks that the content is inappropriate, such as harassment, sexual action, foul language on a website for children. The content will be removed completely if the report is accurate.
Hosting Company: use regulation law or informal request on hosting companies who then must send a deny service signal when user want to go to that specific website. In this case, it depends on the request; the content of the website may still remain untouched or be deleted.
Internet Service Provide: is often done in country-level where governments use their power and forcefully block the information. This method raises many concerns about the freedom of speech and freedom of information, because the blocked information may not be wrong.
Censorship of some countries
In the United States
NETWORK NEUTRALITY 101: Why The Government Must Act To Preserve The Free And Open Internet (2010): The Internet has become a deeply ingrained in the lives of most Americans. It looms so large, in fact, it is easy to imagine that it is immune to change — that it will always remain the free and open medium that it is now. But there are no such guarantees.
Internet Censorship is often conflicting with other exiting regulation or laws in US where human right and freedom are prioritized
Online Free Speech (2006): a clear victory for free speech, the Supreme Court has announced that it will not hear the government's appeal of a ban on the Child Online Protection Act (COPA), the federal law that would criminalize constitutionally protected speech on the Internet.
Online Censorship in the States (2002): In a sweeping victory for free speech rights in cyberspace, the Supreme Court struck down the Communications Decency Act in Reno v. ACLU in June 1997. The Court granted the highest level of First Amendment protection to the Internet, and cyber-activists are still dancing in the streets. Despite the Supreme Court's ruling, states are busy crafting censorship laws at home.
Canada did not specifically regulate about the Internet content. However, local laws do apply to websites hosted in Canada. In 2006 major of Canadian Internet service providers (Bell, Bell Aliant, MTS Allstream, Rogers, Shaw, SaskTel, Telus, and Vidéotron) announced "Project Cleanfeed Canada" -- a voluntary act of blocking of access to hundreds of alleged child pornography sites.
But things had shifted in 2011
_ In October 2011 the Supreme Court of Canada unanimously ruled that online publications cannot be found liable for linking to defamatory material as long as the linking itself is not defamatory.
_ In December 13 and 14 2011, Internet Censorship case finally gets to Court 
Australian government perhaps one of the most active government who want to put the Internet under surveillance of regulation.
In Octobor 2008, the governing Australian Labor Party has proposed to extend Internet censorship to a system of mandatory filtering of overseas websites which are, or potentially would be, "refused classification" (RC) in Australia. This means that internet service providers would be required to block access to such content for all users.
As of June 2010, legislation to enact this policy still has not been drafted. The proposal to introduce mandatory filtering has generated substantial opposition, with a number of concerns being raised by opponents and only a few groups strongly supporting the policy.
The arguments for censorship:
_ It will limit access to some adult content by the general population.
_ Internet users will be able to use a complaint system which will allow them to report offensive websites that can be blocked.
_ Websites that teach crime and terrorism will be blocked
The arguments against the censorship:
_ The web filter will not just block child pornography; it will also block any "RC rated material" which will include blocking access to web pages of banned films, books, hardcore pornography (and video games that do not meet the MA 15+ standard).
_ Material that is illegal to view (e.g. instructions on criminal activity, depictions of child abuse) is a much narrower subset of material that may be classified RC and filtered.
_ The organisation responsible for classifying media in Australia will not be involved in any way in the filtering process- so the filtered material will typically not technically be RC.
_ The web filter will block content that meets the requirements for an MA 15+ rating if the Government disapproves of the access control software on the website offering the content.
_ The web filter will not be able to block peer to peer networks and file sharing programs which are usable for distributing child pornography and allow users to download large amounts of it in a short period of time.
_ The web filter will also block access to websites about politically sensitive issues which have changing criminality statuses e.g. euthanasia and abortion.
_ The web filter may slow down access to the internet; this will contradict the Australian Government's plan to provide faster broadband access speeds.
_ The web filter may be deemed "unconstitutional" under the Australian constitution and may not pass parliament.
_ The web filter can easily be bypassed by a proxy server.
_ The web filter's implementation, deployment and maintenance costs would be footed by the tax-payer.
_ Paedophiles and terrorists use sophisticated techniques to conceal their content from the general public, thus limiting the need to protect people from this largely invisible information.
_ The most common form of child abuse and including child sexual abuse material can be found on YouTube, Facebook and Twitter published by the children it involves, e.g. cyberbullying.
_ The Australian Federal Police will not allow ACMA to filter child abuse material if doing so will tip off criminals to the discovery of their crime.
_ After the Australian Federal Police (potentially involving Interpol and the domestic police of the host country) complete a criminal investigation of child abuse material, the filter will only be effective if the police then choose to allow the server hosting the material to remain operational.
_ It would be more effective to spend the money on cross-border capabilities to shut down hosts of child abuse material at their source
In the People's Republic of China
China is one of countries where the Internet is under heavy censorship. The targets are in all kind of platforms:
Search engines: China request a block that filter search result according to certain terms. Those search engines include both international (ie. Yahoo or Google) and domestic ones (such as Baidu). If the search word is blocked by filter, google.cn displayed the following at the bottom of the page: "According to the local laws, regulations and policies, part of the searching result is not shown."
Discussion forums: Several Bulletin Board Systems in universities were closed down or restricted public access since 2004. In September 2007, some data centers were shut down indiscriminately for providing interactive features such as blogs and forums. CBS reports an estimate that half the interactive sites hosted in China were blocked.
Social media websites: Although the government and media often use microblogging service Sina Weibo to spread ideas and monitor corruption, it is also supervised and self censored by 700 Sina censorsAfter the 2011 Wenzhou train collision, the government started emphasizing the danger in spreading 'false rumors' (yaoyan), making the permissive usage of Weibo and social networks a public debate
Common targets of censorship
Politics and power:
Censorship directed at political opposition to the ruling government is common in authoritarian and repressive regimes. Some countries block Web sites related to religion and minority groups, often when these movements represent a threat to the ruling regimes
Social norms and morals: Social filtering is censorship of topics that are held to be antithetical to accepted societal norms. In particular censorship of child pornography and to protect children enjoys very widespread public support and such content is subject to censorship and other restrictions in most countries
Security concerns: Internet filtering related to threats to national security that targets the Web sites of insurgents, extremists, and terrorists often enjoys wide public support
Protection of intellectual property and existing economic interests: Sites that share content that violates copyright or other intellectual property rights are often blocked, particularly in western Europe and North America. In addition the protection of existing economic interests is sometimes the motivation for blocking new Internet services such as low-cost telephone services that use Voice over Internet Protocol (VoIP). These services can reduce the customer base of telecommunications companies, many of which enjoy entrenched monopoly positions and some of which are government sponsored or controlled.