As a blogger you focus on your writing, your tone and voice, supporting images, the message you share. Design and layout come next. However these last two determine how long a reader stays on your blog. This infographic below shows why.
I can’t emphasize it enough, nr. 3 structure structure structure. Content structure (post categories, archive, excerpt) is really important as it allows your readers to explore your blog better and longer. If they like it, they will come back which is good for your traffic (think of increasing unique visitors).
This infographic is made for company websites, nonetheless it is useful for bloggers as well.
Source: What Makes Someone Leave A Website?