Please post the complete URL for the blog in question starting with http://
If you are referring to a wordpress.com free hosted blog then take note of this – you can’t – it’s not a page – it’s only a tab linked to your home page.
Several themes have a special header tab, usually “Home”, occasionally “Homepage” [*] or “Blog” [**] or an image [***]: that’s not a page such as those you create but a link back to the blog front (the main blog URL, which can be your latest posts or a static page). That tab is hard-coded into the theme: you cannot edit or remove it (except in Bueno, Motion, and Titan). http://wpbtips.wordpress.com/2009/05/06/the-home-tab/