SR Minify HTML compresses the HTML output and removes all new lines, extra spaces, HTML comments, CSS and JS comments single and multiline both and delivers only one single line of HTML code to the client side. This will help you reduce the page size and apparently the load time.
This plugin will help you increase your SEO score.
This plugin will work perfectly if your theme is created in the standard way.
Target template should start with get_header() before outputting.
Your theme footer or end of file should have wp_footer() just before closing body tag.