While this is not a terribly common written error—-although I have at times seen it spelled this way on the information superhighway—-the pronunciation of probably as probly is constant and irritating.
You should probably have a good lawyer if you don’t want to be taken to the cleaners. (not probly)
It’s only an eight-letter, three-syllable word: prob-a-bly. And those syllables are awfully short. If you can’t say the extra –ab, then what do you do when you have to say onomatopoeia—or supercalifragilisticexpialidocious—or antidisestablishmentarianism?
I suppose I should file this one under Pet Peeves.