This means you have to run LaTeX a number of times. Why won't LaTeX generate any output? In Marchversion 0. What a mess. Or sometimes, difficult entries work best when you make judicious use of the note field. Styles provided by Natbib see below handle this field, other styles can be modified using urlbst program.
The standard style's thirteen entry types do reasonably well at formatting most entries, but no scheme with just thirteen formats can do everything perfectly. For example, Google Scholar offers the option to return properly formatted output, which can also be turned on in the settings page.
Here knows where one part ends and the other begins because the tokens in the von part begin with lower-case letters. Since the same style file is used for an entire list of references, these are all formatted consistently with minimal effort required from authors or editors.
I understand that there's often little choice in choosing a bibliography style--journal says you must use ;style; and that's that.
Don't take the warning messages too seriously. It is even possible that lower-case letters may need to be preserved - for example if a chemical formula is used in a style that sets a title in all caps or small caps, or if "pH" is to be used in a style that capitalises all first letters.