Casing Variables, Camel vs Pascal

[sde]

i know of 3 common ways of casing multi-word variables:

foo_bar <-- underscore
fooBar <-- pascal casing
FooBar <-- camel casing

i know it all comes down to preference, but i'm wondering if there is a semi-official difference between when you should use pascal casing vs camel casing.

what do you use?

[Belisarius]

In java, I use firstSecond. In HTML, I use first_second.

[npa]

i sometimes use theJavaStyle

but, generally i will do:
foobar
thejavastyle

i just prefer lower-case letters.

i use the same style for all languages.

i occasionally use underscores; but not often.