wep page close event

Question

hello evryone. i have a problem. i want to make changings on database when user close the web page or web browsser. i want to mmake visitors status offline when user leaves site or close the browser but there is no closing event or sth like closing event. do i miss closing event. i hav another problem a bit diffrent. whenn starting the web site from visiual studio i have no problem about databaase i can edit, delete values on tables. but when i try the web page on my browser calling it from under wwwroot (i published website and placed it under wwwroot)and try to change sth on database tables it says the database is read only. i attach an sql database to my project. how can i make the database writable or editable. i hope i have clearly tell my problems, if i have miswritten sth sory for that