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.

Normalizing the line endings is just making sure that all of the line ending characters are consistent. It prevents one line from ending in \r

and another ending with \r or

; the first is the Windows line end pair, while the others are typically used for Mac or Linux files.

Since you're developing in Visual Studio, you'll obviously want to choose "Windows" from the drop down. :-)