Follow the steps to obtain a more speed result:
1. Disable the AutoGenerateColumns property of GridView
2. Include your field that contains HTML code as a TemplateField
3. Below, edit the TemplateField. Add to it a Literal control.
4. On Literal, set Text property to binding with <asp: Literal id="Literal'" runat="server" Text='<# DataBinder.Eval(Container.DataItem, "fieldNameThatContainsHtml") >' />
PS.: Be carefull with that. Print a HTML code can be dangerous, cause the user can be insert any data in your Request and control your database.