There are following tips you can take care about when maintaining your site.

1. Design Scalable Pages
2. Save All Your Images in a Sub-folder
3. Use Images with the Same Height and Width
4. Create a Template for Designing Web Pages
5. Backup Your Pages
6. Maintain a List of All the Changes to the Web Pages
7. Ensure Your Site Remains Online 24 Hours a Day
8. Check for Broken Links
9. Optimize Your Webpages for Speed
10. Check Your HTML/CSS Code for Errors