The current favorite program for website design is WordPress.
WordPress is not bad but there are a few things you should know.
The first is the reason it is so popular, is because it is fast, cheap and easy for a designer to build a website using it. More profit for the designers. It also gives them an answer to clients' requests to be able to make changes themselves to their websites.
But it has disadvantages too.
It is blogging software. It was not designed for building of websites, but has been adapted to that purpose. Pretty well adapted, but still.
It is easy for a client to make destructive changes such as adding a zillion buttons to the menu. In fact it takes extra work to NOT have a page show on the menu, and to have the home page NOT look like the home page of a blog.
The layout almost always doesn't look quite right, since the whole thing is designed to build pages on an automatic basis.
It is also more difficult to optimize a page (for the search engines) than it ought to be. Matt Cutts, Google's main spokesperson for SEO, has said that WordPress is great for SEO, but that has been widely misunderstood. All he was saying is that it correctly automates SEO for blogs. It is a different story if you are doing a whole website in WordPress or have a blog as part of a site. We know, we've checked the statistics and rankings.
One other factor worth considering is that WP is relatively open to security issues. You have to regularly update your software to deal with issues as they are discovered and patched - much as you do with Microsoft products.
And you don't need WP or another CMS (Content Management System) to be able to make changes to a website. A website designed in Dreamweaver (the most widely used professional design software) can be edited by clients using the companion program Contribute, which is so user-friendly, if you know Microsoft Word, training on Contribute takes less than an hour.