SEO isn;t automatic, but some hosting providers (for example if you went with a hosted CMS such as Wordpress) could make sure certain SEO basics are covered such as alt tags and SEO friendly URL's, however most of the time you'll need to do your own link building and copywriting to build up SEO.
Would recommend getting more familiar with SEO - as a graphic designer working in web it's imperative for you to understand what happens behind the curtain once your design goes to production (I only say this because I work at an agency and it's expected for our guys to understand how SEO translates from their designs when working with clients, it just makes them better designers and clients trust their input because they understand their needs and make it clear through their designs).
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