Add image on post page

Greetings. I added an image (right bottom corner) on my site (angelcorp.net/blog) by adding codes

<div style="bottom:-6.5px;position:fixed;_position:absolute;right:0;"><a href="https://angelcorp.net/infant-formula/index.php?main_page=page_2"><img /*title=""*/ src="//angelcorp.net/themes/stark/Angel-Baby.jpg"/></a></div>

to file “angelcorp.net/blog/wp-content/themes/twentyeleven/content-page.php”. But the image only show up on Pages (e.g. https://angelcorp.net/blog/?page_id=25), not on Recent Posts (e.g. https://angelcorp.net/blog/?p=878). What other file should I add the code? Thanks.