Customizing charts in erpnext

How to reduce the size of charts in erpnext.Please help me.

What do you mean by the size of charts? If you want to delete a account, you can do it from Chart of Accounts, if no transactions made against the account.

reduce scaling of x & Y axis.

Ok, you are talking about charts on top of reports. It is not customisable for standard reports. but if you want to do it for customised reports, please check https://github.com/frappe/frappe/blob/develop/frappe/public/js/frappe/ui/charts.js

http://c3js.org/samples/options_size.html