Content management systems are becoming a bit of a buzz word (or phrase) and are set to become more popular and in demand. They are also a royal pain in the behind since what is perfect for one person is not for another and what works for me might not work as well or at all for your particular needs.
A good CMS meets the requirements of its target user and as such it should be designed with that in mind. In fact, this is a rather good opportunity to draw on a parallel shared with any good program or database design. All good systems are the result of an awful lot of very hard work on many small chunks of the whole. Like any big project, its total is nothing more than the sum of lots of small links in the chain. Get one stage wrong and the knock on effect can bring the whole thing crashing down.
Without going off on one on a software engineering lecture, you basically go through a series of steps to reach your goal state and many of those steps involve evaluating what the system has to do, as well as evaluating how well a prototype or proposed model with perform those tasks. Requirements analysis is everything; if you get that early stage wrong or fail to take into account some of the features you want, you start again or reprogram what you've already done.
Some of your comments seem to indicate that you want the ability to edit page elements (image alignment) as well as the far simpler task of altering page body content text. I notice from your description that you seem to think your requirements are very simple but, in fact, they aren't.
I've programmed several dedicated CMS applications, one very large and three smaller programs, but all of them were to meet a very specific series of needs and requirements, all of which were highlighted early on and monitored throughout the development process.
The point I am meandering towards is that not one of the off the peg solutions is something I'd be entirely comfortable about using without some very serious reworking. Most CMS applications that are freely available are web community portals with little or no real use for running a domsestic or business site. Despite the obvious quality of the code and variety of features, in many cases the application itself is overloaded with included forum, discussion and membership systems and so on.
So no, off the top of my head I don't know of anything that is simple to use with a suitable set of tools to allow you to administrate a website. I know of a lot of applications that include some abilities along those lines, but most are overshadowed by their portal type environment. One of the best CMS programs I've ever seen was a severely hacked version of PHPNuke. It had been recoded in many places to fullfil a set of parameters and worked beautifully, but the three programmers who did the work took weeks to do it and had no budgetary constraints.
All I can suggest is two real possible solutions:
1. Learn PHP and MySQL along with some pretty good software engineering skills and code something yourself to meet ALL of your own requirements
2. Take a look at Sourceforge and see if any of the active Open Source projects will either suit you as is or can be reprogrammed to fit the bill.
There's just no such thing as a simple CMS. The moment you code something rudimentary to do just a few things you think of dozens more that you wish you'd built in, so either you rework or start afresh (refer back to software engineering and requirements analysis comments above).
Take a look at Kevin Yank's excellent book Build Your Own Database Driven Website Using PHP & MySQL
It covers a lot of ground and the lessons learned can be applied to far larger projects than the one used as an example throughout the book.
One of the PCA forum members helped me recently in testing a prototype small-scale CMS and one thing becomes evident even if you can't access the underlying code. The sheer scale of the combination of operations a CMS can perform and degree of control it can offer you over a site mean that it is, by it's very nature, far from simple.
Good luck with it.