There is a hidden feature in Visual Studio. You can add a nice, red, vertical line to your editor.
All you need to do is to create a .reg file with the following content:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0\Text Editor]
“Guides”=”RGB(255,230,230), 80″

And add it to registry (double click). That’s it!