Where do I start?
A very good question.
But, as with any set of directions, it helps to know where you are starting out from. The answer to this question will be quite different for someone who has trained in graphic design and someone who hasn't, because their skills and expectations will not be the same.
Let's make it easy to start with by assuming no specialist knowledge about anything. You know what a Web page looks like, you've seen hundred or thousands of them. Some are plain and simple and some have lots of bells and whistles.
I've seen Web pages put together by eight year old children. It's amazing how quickly they pick it up, but it also proves that it can't be all that difficult.
At its most basic, a web page is similar to a page from a word processor. It has words and maybe some pictures. Web pages are based on HTML (HyperText Markup Language). The 'T' stands for Text and the very first Web pages were just pages of text, with a few bolder headlines and the ability to link to other sections of text on a different part of the same page, on a different page, or another site altogether.
The visual clue that shows that a line of text is linked to something else is that it is usually a different color and underlined. Where a typist might use underlining to emphasise a word or paragraph, underlining text on a Web page means that it is a hypertext link. Using underlining for cosmetic reasons on a Web page can be very confusing.