Most people agree that censorship of adults is bad, most people agree that parents censoring what their children see is good. So, there's ways that parents can censor what their children see.
There's software like "Netnanny", and similar things.
Many of these work by having "unapproved sites". The problem with this approach, is that hard-core porn sites come and go very fast. By the time one gets onto the "unapproved" list, it could have changed its address, and thereby not appear.
There's also something built-in to Internet Explorer.
Go to tools ... internet options ... click on the content tab. Click on "settings". If it demands a supervisor password, then you, or someone else, has already installed censorship on your computer, and you'll need this password to proceed.
When you give it the password, the first thing you'll see is "RSAC rating". This is a voluntary scheme; web sites decide at what level they are for language, nudity, sex and violence. You set the level that you want barred. Provided the web site has decided to use the RSAC scheme, and rated itself honestly, then you'll be barred access to sites that are at that level or higher.
Many of the hard-core porn sites don't bother with getting rated with RSAC. Maybe they haven't heard of it, maybe they'd rather not be barred.
The next tab is "Approved sites". This lets you view sites on this list, even if the RSAC rating is higher than you'd generally allow.
So, you can censor what your children see.
It's also possible that someone has applied censorship to you. If this is the case, then you need to talk to whoever did it, to find out why, and whether the censorship is at an appropriate level. It's possible that an install procedure for something, has also installed censorship. This might have been an ISP's customised install procedure, maybe asking a question like "Family content?" or something worded badly, that you agreed to.