You can download this theme using the link above. This theme was created by Bill Israel, and has been tested for visual consistency in Firefox 2.0, Safari 2.0+, and IE5.5+. Letterhead is a two-column design that still manages to be minimal and readable. Instructions for installing this theme are below:
Download the theme using the link above.
Load the ‘Theme’ settings of your Tumblr account (located under the Account menu)
Select ‘Custom HTML’ from the list of themes.
Copy and paste the theme’s code into the new textarea.
Customize your colors (optional), add custom CSS (optional) and click ‘Save’
And that’s it; you’re now the proud owner of a gorgeous tumblelog!