It occasionally tells me:
"The line endings in the following files are not consistent. Do you want to normalize the line endings?"
Then gives me a drop down with different standards or something, Windows, Mac, Unix, and a couple Unicode.
What the hell does this mean and what is going to happen if I click 'Yes'?
What that usually means is that you have lines ending with something other than a carriage return/line feed pair. It often happens when you copy and paste from a web page into the code editor.
Since you're developing in Visual Studio, you'll obviously want to choose "Windows" from the drop down. :-)
Some lines end with \n
Some other lines end with \r\n
VS suggests you to make all lines end the same.
The file you are editing have been edited with some other editor that does not use the same line endings resulting in a file with mixed line endings.
The ASCII characters in use for line endings are:
CR, Carriage Return
LF, Line Feed
Windows = CRLF
Mac = CR
Unix = LF
It means that, for example, some of your lines of text with a <Carriage Return><Linefeed> (the Windows standard), and some end with just a <Linefeed> (the Unix standard).
If you click 'yes' these the end-of-lines in your source file will be converted to have all the same format.
This won't make any difference to the compiler (because end-of-lines count as mere whitespace), but it might make some difference to other tools (e.g. the 'diff' on your version control system).
There'a an add-in for Visual Studio 2008 that converts the end of line format when a file is saved. You can download it here: http://grebulon.com/software/stripem.php
It's not just VS... it'd be any tools that read the files... compilers, linkers, ... that would have to be able to handle it. In general (for software development) we accept the multiplatform line ending issue but let the version control software deal with it.