How to add a custom css?

What is the best way to add custom css to openerp 7 without modifying any original file of openerp?

Just create a module and add your css file in __openerp__.py as described in the documentation.

 # __openerp__.py
 {
     'name': "CSS Example",
     'description': "new css example",
     'category': 'Generic Modules/Others',
     'depends': ['web'],
     'data': [],
     'css': ['static/src/css/my_css.css'],
 }

Need more info?

This documentation page has been extracted from the Q&A section where you can discuss it and get feedback.
Related question