I do KNOW how to spell ‘language’ but, embarrassingly, I often mis-type it which is a pain as I have to type it a lot.
The most common words I see misspelled these days by the young people are what I would call ‘smooshed words’ where two words get smooshed together incorrectly (yeah, yeah, settle down you crazy descriptivists):
alot
eachother
infront
aswell