Use a element to contain it as follows: Between the opening and closing tags you can place your navigation links ... with transparent background. How to Display Boxes Side by Side in HTML.

You can even make Tumblr posts transparent by modifying the opacity value. Log in to the dashboard. Select the blog from the menu and then click "Customize Theme." Click the "Edit HTML" button.

Fortunately some light CSS tweaking can change its color or make it transparent ... up with your own clever button change-ups, paste the code in the comments, or link us to a write-up.