Many slang words are used on the internet.
Especially on Twitter, people often use them because of the limitation of number of characters.
(You can write much more in Japanese than English though!)
Here are some slang words I often see on the internet.
オタ (ota) / ヲタ (ota)
to search something with Google
copy and paste
*ネタがバレる (neta ga bareru) "the contents are exposed"
A person who enjoys his/her "real life" (i.e. not only on the internet)
*リアルが充実 (riaru ga juujitsu) "the reality is fulfilling"
to buy something on the internet
*ポチ is the sound of click
Have you seen any of them before?
Well, I'll try to make a sentence using some of those words.
(このまえ オフかい いったら ヲタっぽい おとこのこが かわいい Ｔシャツ きてたから、かえってから ググったら ヤフオクに でてて さっそく ポチっちゃった)
I went to an off-line meeting the other day and one otaku-looking guy were wearing a cute T-shirt there, so I Googled it at home, found it on Yahoo auction and I bought it immediately.
Slang is not used in a formal situation and some people don't really like using them. (I think the situation is same as slang in other languages.)
Actually I don't really use them by myself even with my friends either.
But I see so many slang words on the internet and I enjoy reading posts using slang.
For advanced Japanese learners, I highly recommend reading Japanese posts (Twitter, FB, forums... whatever) written by ordinary people in addition to articles, novels etc.
The biggest point which is different from reading serious articles is that if you find a slang word you can't understand, you can just skip it.
That word/post shouldn't be so important.
You can choose some favorite/interesting posts, read them and ignore other posts.
On the internet, you can find short posts very easily and you don't need to "prepare" to read them unlike news articles or long novels.
If you are a Twitter user, Kazu https://twitter.com/arapanman deserves to follow.
His tweets are about politics, news, anime, TV, food, animals... anything and his writing style is not too formal but not too casual.
He doesn't use slang but I see many slang words in his RTs.
(His RTs are interesting, informative or just so funny, too.)
I know him only on Twitter but I enjoy his amusing tweets everyday!
Also for all levels learners, I recommend you post something on SNS in Japanese.
Even if it's a very short sentence, like おなかすいた。"I'm hungry", it must be different from just thinking by yourself.
Maybe you'll get response in Japanese and have a conversation in Japanese.
Maybe you made a small mistake there and will notice it.
Maybe you need to use a dictionary for posting it in Japanese.
For me, I don't really have a chance to use English... I mean I hardly ever have a conversation in English since basically I don't use English in my lesson and most of my non-Japanese friends speak Japanese.
So, having a conversation in English via FB/Twitter is important for me.
At first, I was nervous to post anything in English and shocked to know how low my English skills are.
There are some super bilingual people in my SNS world.
Also some people are very offensive and disrespect (ディスる！) my English/knowledge.
But it's often happened on the internet life anyway, right.
You shouldn't care too much about them if those were the reasons you hesitate to use Japanese there.
Having communication with different people... that must be one of the biggest goal of studying a language I think.
Make maximal use of internet life for communicating with people in Japanese!