Architecture :: Best Practice For Handling Exception?

I devide my website on 3 layers :

DAL(Data Access) - simple extract data from DB using LINQ
BLL(Business Logic) -

cache data and in try/catch block call function from DAL and throw it to UI :
try
{
}
catch (Exception ex)
{
//Log error
throw ex
}

UI (User Interface) - simple working without handling any exception,

So if error occured in BLL i will be redirected to Error.aspx page with message that something wrong.

how and where handle exceptions, or may be exists common patter where handle and how to inform user about errors ? Can anybody share bes practice.