The only part of English that is more difficult and problematic than spelling is the proper use of vernacular phrases.
Thanks to the many words in the English language that sound like each other but have different spelling and meaning, it is really easy to get a common phrase wrong by replacing the right word with its homonym. Sometimes this isn't completely our fault, because the incorrect phrase has actually become the norm, but it's sill wrong.
The following infographic lists 8 common phrases that I have seen people misuse.
Edit: I have updated the infographic to replace "begging the question" with "baited breath". The second term makes for a more coherent graphic.
On a related note, this is my first homemade infographic.