Online and offline are hyphenated inconsistently: "online" is spelled as such in most places; "off-line" is spelled as such in most places. This makes things look weird when the two are displayed side-by-side, as on the site maintenance page for instance.
I suggest that online stay the same and off-line drop its hyphen. Rationale:
- Online is most commonly used today as an unhyphenated word (by my judgment and Google search); on-line seems stilted.
- Offline is also most commonly used today as an unhyphenated word (by my judgment and Google search). It is recognized by the American Heritage Dictionary as the first spelling, Random House Unabridged Dictionary as the second spelling, and Merriam-Webster as not a spelling at all. So dictionary opinions vary, but it is recognized as valid by the majority.
- Dropping the hyphen will save bytes. (just kidding)