Rules can vary depending on which style book is being used.
AP STYLEBOOK (journalists)
http://www.apstylebook.com/,
Chicago Manual of Style http://www.chicagomanualofstyle.org/home.html and
Modern Language Assoc. or
MLA http://www.mla.org/style_faq1(latter two for academic works).
The OWL at Purdue is a wonderful site; easier to follow than most. It has a special section for Professional Writers in Business:
http://owl.english.purdue.edu/owl/resource/681/01/
It's important to note that internet writing is changing things. Shortcuts and simplicity are shifting some rules. Several are shared in writing guidelines and in forums.
But
basic rules for titles and captions:
Do Capitalize:
FIRST and LAST words in a title or caption.
ALL IMPORTANT words.
NOUNS, PRONOUNS, VERBS, ADVERBS, ADJECTIVES and
SUBORDINATING CONJUNCTIONS (e.g. That, Because, As)
Don't Capitalize:
COORDINATING CONJUNCTIONS (e.g. and, but, or)
ARTICLES (e.g. a, the, an)
PREPOSTIONS less than FIVE LETTERS (e.g. of, to, from, at)
SMALL words (e.g. do and the ones above. N.B. Many will capitalize "Do."
The
US Gov't Printing Office Style Manual states:
"Capitalize all words in titles of publications and documents, except 'a, an, the, at, by, for, in, of, on, to, up, and, as, but, it, or, and nor'."
In your first PayPal example, the last word, "It" should be capitalized.
Hope this helps.
