Human beings are creatures of habit and the more things remain the same the more we trust them. Part of convincing your customers to trust you is about making your blog look the same every day. The type size and font should be the same, links should be highlighted the same way and your images should never change. You can always change the content but you must be reliable in terms of appearance.
Consistency and sloppiness are at opposite ends of the spectrum. People would not read a newspaper that had horoscopes in the sports section and obituaries in the cartoon section. Each time your visitors come to your site, they should know what to expect and where to find things. Make sure to fulfill this expectation by making sure your site is well organized and that all the links work. This means being very dutiful about your site maintenance.
It might be valuable for you to write yourself up a little style guide that defines how you will define the little things and keep them consistent throughout the entire site. These are the rules that you will always stick to each time you make a new blog entry. For instance, will you be spelling website as website or web site. How will you treat your headlines? Will they be in all caps, bolded or in another color? If you use bullet points in blog entry will they be asterisks or dots? These might seem like small matters but keeping all of this stuff in mind can help your site have a more professional, cohesive look in the end.
Another point of consistency is in the layout of the blogs. Each entry should looks similar. The headers and fonts should all be the same size in every single entry. If you insert an image it should always be in the same place on a page.