Reasons For Blocked Websites That I've Accidentally Encountered

Listed in order from most sensible to most ridiculous.

Parked Domain:
This was the official reason but it went on to explain that it had a higher potential for viruses and such that could harm the computer so it seemed perfectly reasonable and necessary.

Explicit Content:
Thanks for warning me that something was not safe for work. Funny thing is though, the computer cannot recognize things that have NSFW in the title which would probably be something worth looking into.

Nudity:
I definitely get it but I'm pretty sure I got this message when the nudity was of an artistic nature and completely asexual. I guess either way it should be blocked in a work context.

Lingerie/Swimsuits:
We were girls looking at swimsuits. I wonder if men's underwear and swimsuits gives you the same message? Strangely enough, this is the easiest block to get around as people have proven to me.

Social Networking:
You're at work, you shouldn't be socializing. However, it's a bit odd that LinkedIn is taboo but any specific Tumblr page isn't.

Games:
Just as distracting as Social Networking. Really the big problem with this one is that it doesn't let you read gaming news either so stuff like thoughtful essays on the misogyny and racism involved in Gamergate is also off limits.

E-mail:
Yes, you're at work and this is a personal matter but there could be a legitimate reason for needing access to a personal e-mail at work.

Gay/Bisexual Interest:
Since when is something homosexual inherently sexual or wrong? I was just trying to read an article on hate crimes.

Non-traditional Religions:
Computer, I thought you were being homophobic with that last one but now I'm positive you don't like people different from yourself. The best thing about this one is that it came up when I was trying to look at a Celtic clothing website. Aside from being discriminatory, the site only had a witches datebook and a pentacle necklace alongside over twenty cross necklaces. Also, Wicca comes from paganism which is older than Christianity so your argument is invalid.

Tasteless:
Apparently taste isn't subjective and Cracked.com is unacceptable.

I will update this if I encounter any new ones.