<img id="logo_topo" class="img-responsive" src="<?php bloginfo('template_url'); ?>/imagens/logo.png" alt="Logo" />

src="http://localhost/site/wp-content/themes/site_tema/imagens/logo.png"

src="/site/wp-content/themes/site_tema/imagens/logo.png"

<img id="logo_topo" class="img-responsive" src="<?php echo get_template_directory_uri(); ?>/imagens/logo.png" alt="Logo" />