Font sizes are controlled via CSS, and are explicitly set in em values for numerous selectors. To perform a re-sizing across all elements, use the body selector and set a value via Custom CSS. For example, the following snippet will reduce font size across all elements by 5%:
body {font-size:.95em;}
If you’d like to tweak individual elements, you’ll need to use a more specific selector.
The custom CSS window should be empty, unless you’ve added your own CSS styles. The CSS for the theme is contained in an external file, which is occasionally updated to accommodate fixes and improvements. The current version of the CSS file is 1.3.
An API key is not provided by default with your Twitter account. This is an advanced feature and requires registering your blog as an “App” with Twitter. For more information regarding Twitter’s API, please visit their developer site.
Yes, using custom CSS. The theme uses id’s to dynamically adjust the width of each column, depending on page type. The left, center, and right columns are labeled with the following id’s respectively: #sidebar, #primary, and #secondary. Here is the CSS that controls column width:
#sidebar { width: 200px; }
#primary { width:669px; border-left: 1px solid; }
#index #primary { width: 438px; border-right: 1px solid; }
#permalink #primary { width: 538px; border-right: 1px solid; }
#secondary { width: 0; display:none }
#index #secondary { width: 230px; display:block; }
#permalink #secondary { width: 130px; display:block; }
This gives three possible layouts: All three columns (e.g. home page or tag index); all three columns, but with a wider center column and narrower right column (e.g. permalink pages or ask page); two columns, left and center only (e.g. pages).
Column widths may be adjusted by tweaking the styles via custom CSS, however please note that the theme uses fixed sizes for photo, photoset, and video posts to correspond with the default column widths. Adjusting those requires tweaking the appropriate theme tags.
As for font sizes, custom CSS can again be used to adjust the default settings. Each column may be individually targeted using the #sidebar, #primary, and #secondary selectors, as well as individual elements using more specific selectors.
Darken Your Palette

The default color palette for Headline is designed for dark on light tones. If you’d like to switch up your look, and go for light on dark, here’s a good starting point. Remember, all these values are accessible under the Appearance menu, in the Customize sub-section of the Dashboard:
Background color: #1A1A1A
Background Alt color: #222222
Site Title Text color: #EFEFEF
Body Text color: #CCCCCC
Meta Text color: #666666
Sidebar Heading Text color: #999999
Navigation Text color: #666666
Text Shadow color: #111111
Links color: #00CCFF
Borders color: #333333
One final note: be sure to clear the default background image, otherwise your updated background color won’t be displayed!
Adding a Custom Header Image
To add a custom header image, you’ll need to navigate to the Appearance tab in the Tumblr Dashboard, which is located in the “Customize” sub-section.
Once inside the Appearance tab, you’ll need to scroll down a bit and look for the “Header image” label. By default the Headline theme does not contain a header image. It uses your blog’s title as a header. To add a header image, click “Upload” and select your custom graphic.
Please note that the maximum width of the theme is 870 pixels. If your custom header image is wider than 870 pixels, it will run beyond the third column and not look very good. For images less than 870 pixels wide, the image is centered.
For you CSS-savvy users, please note that a top and bottom margin of 1.5em is added to the #header-image element. If you’d like to flush your image to the top of the page and left-justify it, you’ll need to override the defaults using the following custom CSS:
#header-image { margin-top:0; }
#header {text-align:left; }