Search engine optimization specially focuses on the theme which you are presenting through your website. A website is a complete introduction of your business or product, if you are successful to provide the information in a great way definitely, you will advertise your business or product in a better way. If you are not presenting your goal in a proper way and it is unable to grasp the attention of the reader; you can not gain anything from your web page. Search engine optimization tells you that you have to follow the tactics that may get the concentration of the internet user as much as possible. You have to have full grip on the topic otherwise you may loose your customers or clients.
Now a day all the themes are updated according to the google guideline and policies but few of them are not. So be careful while theme selection.