"Supposably" is not a word.
Not even when spelled "supposebly."
So please refrain from saying it. Instead, I think you mean, supposedly.
Other non-words to avoid saying or spelling.
*definately (it's definitely spelled "definitely - yes, Mom!)
*ezackly (submission from Mrs. Potter)
Feel free to comment other pet-peeving non-words.
No, I'm not a Nazi. I just don't like for you to sound dumb when addressing me or others in public or private. I'm just looking out for you!