I think I know what may look strange about the capitalization of this title. First, here is a good guide (there are many others if you search for "title case"):
So, "a" and "the" are not capitalized because they are articles. But what about "on"? That's a preposition, isn't it? And according to this (and most) style guides you don't capitalize prepositions.
But in this title, "on" is not being used as a preposition. It's part of a compound verb, "catching on". Verbs are capitalized, so both those words are capitalized. Another good clue here is that "on" is the last word in the title, so it's not likely to be a preposition ("pre-position").
There is a subtlety here: "catch on" or "catching on" is often a compound verb meaning "becoming popular", but in a different context, it may be a simple verb and preposition. Consider these two headlines:
Sticky Notes are Catching On (becoming popular, "catching on" is a compound verb so both words capitalized)
Sticky Notes are Catching on Tables (getting stuck to tables, "catching" is a simple verb and "on" is a preposition, so "on" is not capitalized)
http://www.grammar-monster.com/lessons/capital_letters_title...
So, "a" and "the" are not capitalized because they are articles. But what about "on"? That's a preposition, isn't it? And according to this (and most) style guides you don't capitalize prepositions.
But in this title, "on" is not being used as a preposition. It's part of a compound verb, "catching on". Verbs are capitalized, so both those words are capitalized. Another good clue here is that "on" is the last word in the title, so it's not likely to be a preposition ("pre-position").
There is a subtlety here: "catch on" or "catching on" is often a compound verb meaning "becoming popular", but in a different context, it may be a simple verb and preposition. Consider these two headlines:
Sticky Notes are Catching On (becoming popular, "catching on" is a compound verb so both words capitalized)
Sticky Notes are Catching on Tables (getting stuck to tables, "catching" is a simple verb and "on" is a preposition, so "on" is not capitalized)