Within any blog platform that we have talked about before, you will have many choices of themes. The mistake many people make is to choose what looks like the easiest and quickest theme that comes along and call it “good enough”, when they should be looking a lot deeper than that.
If you are only looking at a blog to be read, it is not as important as choosing a theme with the proper components to use as a sales site. However, looking at the future use of the blog at some point down the road is more important than just putting something out there to get started.
Most blog themes allow the colors of the page to be changed, even on Blogger. The colors should always reflect the topic of the site. The topic of gardening would usually suggest something in green and brown tones, in other words, earthy colors. A topic of cars or mechanical things usually works best with "tool box red" and black, or even yellow and black. More general topics can never go wrong with something in shades of light blue, as that is usually the color that is easiest on the eyes as a background.
Of course, if you have a particular logo with colors in it, you want to always choose a background with accents, rather than clashes with, your logo colors. If you use a photo in your header, you want to choose something that will go well with the rest of your site. Any other add-ons, such as photos and banner ads, can usually be chosen for their colors, so that they compliment the colors in your site.
The one thing that nearly everyone agrees on is that dark background colors and bright text are hard on the eyes, and yet there are many themes out there that are designed specifically for these colors. For topics like rock music, motorcycles, and "dark" subject matter, this can be appropriate, but be careful of the layout. Don't overwhelm people with long blocks of text to read. Try to keep the text bright, larger, and to a minimum. Make sure you leave plenty of paragraph breaks, and use lots of images to break up the dark background. Those images can be photos, or even banner ads. Adding changes of color to any background helps to break up the monotony of long blocks of text, and makes the page more visually appealing.
Anyone can do the research to see what the easiest fonts are to read, but usually something in Century or Arial (or something close, like Verdana) is the easiest to read. I have seen many themes that include some form of fancy script, and usually will not even waste my time trying to get through it. That isn't just my opinion, but that of anyone who has ever done marketing studies to attract the most people. In some cases the font can be changed within a theme, but depending on how the blog is set up, it might be easier to just choose a different theme.
The size of the font is also important. I have seen some sites that have such small font, that I refuse to even read them, let alone try to follow their posts. ALWAYS... think about who your readers are, and what devices they may be using to read your site. Normally, the older people get, the worse their eyesight becomes. If your target audience is an older age bracket, then choose something with a font that is large enough to read without a magnifying glass! Again, some font sizes can be changed in the theme, but it may take tweaking the code (only doable in the dot org version of Wordpress). If that is beyond your current expertise, then the easiest thing is choose a better theme!
Themes come in all sorts of varieties, and all kinds of standard layouts. In many of them, you can choose how many columns you want (which also includes the sidebars). Most blogs will only need two columns, which means a wider post column, and a narrower sidebar. Studies have shown that is it most advantageous to put the wider column on the left, as people generally read left to right, and their eyes go to the most important information first. For casual blogs, that is normally enough.
For certain marketing applications, where the author intends to use a lot of sidebar gadgets/widgets (they are same thing, and are only called different names by the different blog platforms) containing ads or other information, they may want a third column. That could mean a narrow sidebar on either side of the post, or in some cases, a wider post column to the left followed by two sidebars on the right, or even vice-versa.
Gadgets or widgets are the little building blocks of most blogs, and most are already programmed to do certain things, such as add a subscribe form, a search form, add social buttons, an archive of past blog posts, etc., while others are more generic, allowing you to add your own text or html language to perform other functions, such as adding a payment button. Typically, they will remain standard and show on every page of your site without having to install them on every page. On Wordpress blogs, you can install plug-ins to give you many more choices regarding how the widgets show up, but most bogs will not do that.
The placement of the widgets is also important, especially when you get into marketing. Most blogs will only allow the placement of the widgets in certain places. Here's an example of a glitch we have run into...
Because of the way sites display on mobile devices, the sidebars do not always show up at all, so if you have ads in them, or even a list of your archived posts, people on mobile devices will never see them! The only thing most of them see is your header (often without your header photo) and the main blog post. The only way to get people to see these other things is to include them in the body of every single post you write, which takes a lot more work!
Here's something else we just noticed this morning... when we looked at one of our blogs on my smart phone, and clicked on the "View as web page" link at the bottom of the post, it showed the widgets in the side bar, but still failed to show the footer widget at the bottom of the page! I think this is an error in the way the blog was set up. Why it reads widgets on the side and not on the bottom is anyone's guess... but things like this happen! And it's why you should always look at your site on various devices and different browsers, to see how it is showing up! Either one could change the font style, the layout, and affect other things. Your goal is design the site so it appears as well as it can across the board, on all browsers and all devices if you expect to hang onto your readers!
Some blogs will allow you to add a widget to the top of your post, but that still doesn't mean it will show up on a mobile device. This is where the technology on one hand hasn't caught up with the technology on the other hand! Before mobile devices came along, there wasn't a problem. But as of a few years ago, the number of people accessing the web through mobile devices passed the 50% mark, and today, they are far in the majority of all users. If we don't satisfy the needs of the mobile market, we will automatically lose most of our readership, and if we are monetizing our sites, we also lose a good percentage of potential income!
Much of the problem lies in the smaller size of the mobile screens. In order to keep the fonts somewhat readable, the information can't all be jammed onto the screen at the same time. The engineers and designers have decided that the best way to alleviate reading problems is to show only one column at a time. But some sites and themes will allow the rest of the site to be seen if you keep scrolling down past the initial post, and others won't. The latter seems to block ALL widgets, regardless of where they are placed... even at the top of the post column.
This is something that I hope the industry in general will correct as time goes on, but for now, we have to figure out ways to do "work-arounds" to these problems. It could mean testing each theme on a mobile device before we actually choose on that will work the way we need it to work!
It would be impossible to come up with a list of all the browsers, devices and themes that are completely compatible with each other, as the developers are fixing many problems after the product has been released and tested by the public.
I have mentioned the main things to watch for in choosing a theme, and why you have to be careful in what you choose. I have seen many third-party paid themes and plug-ins designed for Wordpress that the developers were too much in a hurry on to test them out thoroughly. Often the greed for profit over-rides the need for perfection, they leave it up to the public to do the testing, and make the corrections as they are reported to them.
As always, if you have a question on anything, post it in the comments. I will take a look at your site and make my recommendations on it free of charge.