Home page does not have a 'page ID'

I am using twenty-eleven theme, and am using the ‘pages’ side widget. To exclude pages from the side widget menu, you must enter the page ID. The home page is just:

http://www.duraglaze.co.nz

Other pages have ?page_id=38, for example so I just write ’38’ to exclude that page. How do exclude the home page?

By the way, I know someone will notice I’m not using ‘pretty’ permalinks, but when I do that some of my pages won’t open