One common issue may bloggers (and web site) owners must consider is the design interface of their blog. Your design is the packaging to your product (the content). Much in the same way that companies like Sharp, Nike, Coca Cola, etc., pay attention to professional brand packaging, we need to do the same.
Remember, if your packaging (blog design) looks unorganized, ugly, "busy", disorganized, etc. then that's the message your sending to potential users. In other words your design is telling visitors a fair bit about your blog, before they even read the content. If the blog looks terrible or is not functional, you'll probably lose that visitor. A blog with horrible typography (fonts), positioning or navigation is a clear message to readers saying "I don't have attention to detail, I don't care about quality, I am not professional". After all, would you go to a wedding with dirty worn-out jeans and a soccer tee-shirt? Of course not!
Having said this, let's pause for a moment and consider that design is not just about the graphics on your blog but more importantly, design is about planning and functionality. And in my opinion, graphics take a back seat to the functionality ...