Perhaps MSDN's Nonstandard Behavior page for Visual C++ will enlighten you? Make sure you look at the version you're most interested in (the box on the right-hand side).
Since MSDN's links change all the time (and who knows why), here's the main content from the page on VS2008, so when the link breaks and someone comes across this answer, they can Google and find the correct page:
Nonstandard Behavior
The following topics are some of the
known places where the Visual C++
implementation of C++ does not agree
with the C++ standard. The section
numbers refer to section numbers in
the C++ standard.
- Compiler Limits
- 10.3 (Paragraph 5) Covariant Return Types
- 14 export Keyword on a Template
- 14.6.2 Dependent Names
- 15.4 Function Exception Specifiers
- 16.3.2 The # Operator
- 21.1.1 Character Traits Requirements
- Storage Location of Objects
