Nav bar not right?

Not sure what is happening here, but my nav bar is getting cut off and pushed down? I am using the blog directory plugin too if that matters.

Here is the error I get when I hit the auto populated Blogs page from the plugin

Fatal error: Call to undefined function is_subdomain_install() in /home/content/00/5747600/html/biz/wp-content/plugins/blogs-directory/blogs-directory.php on line 264