WebSite Performance decreasing due to more records in gridview

Hi,

In my website need to display 5000+ records in gridview. So, I used custom paging for static page bar and displaying 100 records per page. In stored procedure using ROW NUMBER() keyword to retrieve specific records from the database. Even though website is running dead slow. Is there any alternate way apart from the ROW NUMBER() to increase the website performance.  Can anyone please suggest me...It is very critical for me. ...I followed the below article to achive custom paging.