Find the line of code that reads "font-size:" and then a number. Changing the number will increase or decrease the size of the header font, with the higher numbers resulting in larger fonts.

Fortunately, Tumblr enables you to change the font size for your blog's text by giving you direct access to the raw CSS or Cascading Style Sheet code of your theme.

Here's how you can change the font size in the Mint Menu in Linux Mint 12.