Here's why:
* Homographs are words that are spelled the same but have different meanings and sometimes different pronunciations.
* Homophones are words that sound the same but have different spellings and meanings.
"Content" can be pronounced with two different stresses:
1. CONtent (adjective): meaning satisfied or happy.
2. conTENT (noun): meaning the material that makes up a book, website, etc.
Since "content" has different meanings and pronunciations depending on the stress, it is considered a homograph.