Try modifying the header section a bit to comply with the standards. Here is what your code right now:
<img width="1102" height="350" alt="" class="header-image" src="http://onofri.org/example/wp-content/uploads/2013/06/header1.jpg">
Here is how you can modify the things:
<a href="<?php echo esc_url( home_url( '/' ) ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
<img src="<?php echo get_template_directory_uri(); ?>/images/logo.png" alt="Logo" width="HERE" height="HERE" />
There are only 3 steps now:
- Instead of using the theme's default header image settings, you can edit your theme's
header.php with the code given above.
- Instead of inserting image from the Add New Media, you can upload image via cPanel (Control Panel of your web host) into the theme folder's sub-folder named 'images'.
- And instead of making a huge image with background for your logo, try making a simple background-less logo in Photoshop (or any graphics software) - in case of Photoshop, just do it: after placing the logo image in a layer, just delete the background layer and then save the image for web (File > Save for web... [Ctrl + Alt + Shift + S]) and choose the format PNG-24 for a good result. Then save it as
logo.png and place it to the '/wp-content/themes/simplemarket/images/' folder.
Hope you get the rest. If any question, please feel free to comment here under.