Use this web page to generate cursed text l̷̳̇ï̶͓k̷̦͊ë̵͕ ̴̜̌ṫ̷͔h̴͍̄i̶̥̕s̶̩͌. You can copy and paste the cursed text into chat messages, internet comments and all sorts of other places. To people who don't know about it, it can look creepy - as if you've hacked the website. In reality, however, it's just a slight abuse of the Unicode standards which allow "diacritics" to be limitlessly "composed" together, since some languages require this.
Some people call this "satanic text" or "demonic text" or "void text" - they all mean the same thing; text that has been "messed up" with diacritic marks so that it's hardly readable. As a bonus, Unicode allows diacritics to stack to heights the cause the text to overlap with the text above and below. This increases the "hacked" appearance because it appears as if some websites are broken because text is overlapping in weird ways. This hacked text effect is great for scaring 10-year-olds in YouTube comment sections into thinking that you're a l33t hacker who is to be feared lest you "hack into their mainframe" and make their computer explode or something... I don't know.
Some website owners of large sites have began to "crack down" on this text though because it makes their websites look broken. So if you copy and paste this cursed text stuff into a website's comment section (or wherever) and it doesn't work, then that's probably the reason.