put in web2py/applications/YOURAPP/static/css/yourcssfile.css
refer with
<link href="{{=URL('static', 'css', args='yourcssfile.css')}}"
................../>
--
put in web2py/applications/YOURAPP/static/css/yourcssfile.css
refer with
<link href="{{=URL('static', 'css', args='yourcssfile.css')}}"
................../>
--