View White Space

Use the following Menu in Visual Studio to view the white space characters
Edit->Advanced->View White Space
This allows you to see whether the white space is tabs or spaces.

For me these characters are too prominent. So I dim them by choosing
Tools->Options->
Environment->Fonts and Colors
Select "Visible White Space" from the Display Items.
Select Silver. Then Click the Custom Button and use the darkness scale to choose the right amount of darkness.

In Beyond Compare you can select the following from the View menu:
Show White Space
Ignore Unimportant Differences

They are useful when dealing with differences in white space.