You have incorrectly edited the file containing the name of the logo.gif. The browser is trying to leave room for the HEADER_LOGO_IMAGE but is not getting the correct define. That's why a look at the inspect for your main page shows the image source for the logo to be
Code:
<img src="includes/templates/template_default/images/HEADER_LOGO_IMAGE" alt="" width="500px" height="12px">
As the mobile version cannot see an image, it makes sure to leave room if a logo.gif ever shows up. Thus the blank box.
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