How to do CRUD operations in Microsoft Dynamics CRM using html page

I want to do CRUD operations through HTML page without adding that page in Dynamics CRM's webresource(need to access crm from another web application).

Using C# we can connect with Dynamics CRM and can do get/add/edit/delete operations using CRM's dlls but I don't know the way of doing same from html page which is independent from CRM's webresource.

Can anybody please suggest me that is this possible or not and if yes then the way if there is any.