Thanks Danimar Ribeiro,

Alredy i did the same, my addons path structure is like

/opt/smartcampus/odoo/openerp-server --addons-path=/opt/smartcampus/odoo/addons --db-filter=College_Demo --xmlrpc-port=1504

but still i am facing the same issue.....

The custom css is only applied when the database is selected.

To resolve the issue you have to set a default database in the parameter "db_filter", 

after this when you go to your url the odoo automatically selects that database and loads the installed module with your custom css. Without this it doesn't know which database to load the modules, so your moduleis not loaded.