Strange black line under Wordpress logo

[Jiko]

I am building my own website using Wordpress. When I was using a PNG picture(140*82 px) instead of the default "site-title" as my site logo, I got a really strange result. The picture is presented nicely, but there is a black line just under the picture. I have checked my "header.php" and "style.css" file, nothing wrong there. I also used Chrome "Inspector" to check the logo, it said: img 140*83( natural 140*82 ).So, where does this line come from? Thanks, guys!Here is my logo section in "header.php":\[code\]<<?php echo $heading_tag; ?> id="site-title"> <span> <a href="http://stackoverflow.com/questions/15562159/<?php echo home_url('/' ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>.com" rel="home"> <img src="http://118.228.173.234/wp-content/uploads/logo.png" width = "140" height = "82"> </a> </span> </<?php echo $heading_tag; ?>>\[/code\]