A template must follow some specific guidelines such as well defined heading tags for post titles. Proper nofollow and dofollow links site-wide.
Theme Responsiveness is a new SEO criteriaMajority of people, today, browse the web from their handheld devices such as mobiles, tablets etc. For that matter, a blog theme must be designed in a way that it looks user-friendly on all handheld devices across all resolutions. A template that does all this, is called a responsive template. Major search engines including Google, consider responsiveness as a criteria for good search engine ranking. So, you must select a theme for your blog that is not just well written, but also is responsive and works fine across all devices including mobiles, tablets, laptops etc.
Whenever you buy a blog theme, must check prior to purchase if it works fine across all handheld devices, must check theme responsiveness. You can explore more on search engine optimization from our well document guide to seo that is written for beginners as well as SEO experts to polish their optimization skills and learn latest techniques to rank well in search engines.