There's not really a lot of point in creating websites with applications like iWeb, or its rivals, anymore. I wouldn't recommend any of the drag and drop style software that's around just now or the online websites builders. Some of the latter can produce responsive websites that will adapt to mobile devices but they still use too much code to be viable alternatives to actually learning how to do it yourself or using a stylesheet incorporating media queries.
Unless you have been on another planet for the past two years your will have noticed that the number of people surfing the net on mobile devices has been increasing rapidly and is set to overtake those using computers. Computer sales are falling and, in many cases, are being replaced by mobile devices. You only have to look at the initial sales of the iPad Mini to see where the future lies.
Applications like iWeb cannot build websites that are suitable for viewing on mobile devices. The way in which we use code is changing too. HTML is now very simple with the introduction of HTML5 and shouldn't take but a day or two to learn the basics. CSS is where you need to apply your learning efforts since its newer features are taking over from flash.
jQuery mobile is really advanced now and only requires a limited knowledge of HTML and pratically no CSS if you use the ThemeRoller. And its absolutely free!
Here's an example showing many of the features available and how a responsive site reacts to changes in browser or device width...
http://mobile.ezmacwebdesign.com/