According to the browser, the gap visible in the jsFiddle link is actually a part of the font itself. For example, inserting a lower case g
into the text would make the bottom gap disappear and align the span with the rest of the text.
Unfortunately, there is no automatic way for browsers to resize the text to remove this gap since they are unaware of the specific threshold. This means that manual adjustment through trial and error would be necessary, but this method may not work consistently across different browsers.
The most feasible solution to address this issue and eliminate the gap would involve using an image instead of text.
If you prefer not to create the image using software like Photoshop, another option is to generate the image dynamically on the front end using canvas or on the back end with a library such as GD in PHP. By generating the image dynamically, you can easily edit the pixel data to remove any whitespace around the text.
Additionally, utilizing a font replacement technology like cufon or typeface.js could potentially provide text without the gap by making some minor adjustments.