The first time I designed a site about 10 years ago I used tables to do my layout and to construct the web pages of the site. Which for the time it was the latest technology for designing web sites, by putting tables within tables which is called nesting tables but proved to cause the web site to load slowly. This also caused the visitors to see the site differently in different browsers, so if you viewed the site in Internet Explorer it would look a certain way and if you viewed in another it would look completely different. Well, now the only way you should layout a site is using CSS (Cascading Style Sheets).
Why you ask? Well, I am going to let you know. The first and most important thing about CSS is that it is by far more compliant when developing for multiple browsers; you can control not only the web layout that your viewers see in their browser but you can control how a web page is printed, how it is seen in a mobile device, or even how it will be seen on TV. CSS allows you to control so many aspects of your web site; you can control link color, font types, font sizes, font color, page background color, positioning of columns and positioning of content. These are just a few of the many ways you can control your web page and other web related content.
If you are a beginner and want to know where to start I am going to provide some links below. My recommendation is that you start by just controlling simple content on your site like fonts, link color, and text. Learn the basics first what can you control and what you cannot control, what will be seen in browsers correctly and what will not. IE (Internet Explorer is notorious for CSS not working correctly and requiring special CSS just for IE to show the web site in the same manner as the other browsers. W3C is a great place to learn the basics and do some tutorials that will teach you the basics as well as more advanced CSS techniques.
One important piece of advice that I can give when designing a web site for a client, customer, or even for yourself is to study as much as possible and do as many tutorials as you can. Here is a list of links that I have used to teach myself as well as links that I referrer back to when designing a site for a client. However, always keep in mind what browsers your site will need to work in; such as, Firefox, Opera, Safari, Chrome, Internet Explorer and as you become more proficient you will need to decide what level of CSS you are going to do use and whom your audience is going to be.