Kirk Wight

Your problem is with the URL to the button image, called “prev.png”. Most likely you need to add get_stylesheet_directory_uri() to your image URL in navigation.php. If the button is in a folder called images inside the theme folder, you would need:

<img src="<?php echo get_stylesheet_directory_uri(); ?>/images/prev.png">

That conditional PHP code looks a little wacky to me… easier to insert the_title only if we are not on the home page:

<?php if ( ! is_front_page() ) { the_title(); } ?>

It looks like it’s maybe intended for a featured image, but isn’t coded to skip if the image is not set.

The empty img tag is there in all the browsers, you just can’t see it in IE9 and FF.

If you don’t care what it is, you could just add

.post-image {
    display: none;
}

to your style sheet to get rid of it, or delete the code that’s trying to insert it in the first place (maybe in index.php or loop.php?)

+1 for alchemyth’s answer. You could even use the post_class() parameter in my example above, see “Add Classes By Filters” under Examples here: http://codex.wordpress.org/Function_Reference/post_class

You can replace the current #content with this in your style.css:

#content {
  border-right: 1px solid #EEEEEE;
  margin: 0 240px 0 20px;
  padding-right: 40px;
}

Assuming your theme uses the_ID() when outputting the posts:

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>

you can target individual posts with CSS:

#post-1 {
    background: green;
}
#post-2 {
    background: blue;
}

Under Gallery > Options > Images, just uncheck “Cache Single Pictures” and then clear the cache folder.
Not sure what that’s all about, but as long as this setting isn’t important to you, it will avoid having to change plugin files after an update.