I am designing websites for around 7 years, but more intensively since Joomla was introduced (even though, Joomla! was not the first CMS I used, it was Expression Engine). Why Joomla?
I've been asked this question over and over again, expecially since Wordpress gained popularity and became widespread.
Many web solutions are developed for Joomla! to simplify work. I personally rely on Gantry Framework. Among number of good framework systems, for website design and creation I place this excelent framework in the first place. It lacks a detailed user interface design system, but extended posibilities of coding make up for this imperfection. We shouldn't neglect other frameworks: T3, Expose, Vertex, Yougrids, Warp which I tested and presented in one of the articles (5 most popular theme frameworks for Joomla).
When talking about websites, I didn't limit myself only on website creation, but also on SEO, (I was employed as an SEO specialist for two and a half years). In 2014. I cooperated in the startup project called StepUpIT and lectured at the College of Slavonski Brod on web programming (html, css, php, jquery, Joomla, Web shop, SEO).