Do you have custom code in the project that uses this LogGenerator class?
If you do, remove it :)
LogGenerator is used in older versions for generating statistics on how many page views you have per page on your website. Normally you don't use it...
You don't need it for using log4net no...
To get statistics on usage, use GA (Google Analytics) instead...free, and a thousand times better. There is a nice addon to give Editors information about statistics directly in edit mode and on dashboard.
Hope that helps!
If it helped you, feel free to mark it later as answered to let others know it. Good luck!
But when I am migrating it from 6.1 to 7.0 getting below mentined error in code.
The type or namespace name 'LogGenerator' does not exist in the namespace 'EPiServer.Web.WebControls' (are you missing an assembly reference?)