Question on front-end developing

Learn them and apply them well on websites to prove as experience, nowadays you need to be able to work with responsive designs 100% and they are asking for some SEO experience. Sites today are all about SEO and you need to know everything about it to make your site SEO friendly.
I am a front end developer and in my country the core things you need to know WELL are HTML, CSS, and JavaScript, its great if you also use design programs like photoshop and illustrator.