The most important criterion of a successful website is precisely whether it accomplishes its intended objective. Websites don't have to be cutting edge or beautiful in order to be functional, compelling and successful. Take Craigslist.org as your prime example. No offense but I have seen very few websites as bare and conventional. I personally don't like its visual appearance; but Craigslist is as successful as any site can ever be. This is precisely because it was intended and guided to meet a certain objective and it was accomplished.

The easier you make it for users to accomplish what they are looking for on your website, the more successful it will be.

Have you ever heard of AIDA?
AIDA is a method specifically used to guide visitors to take a specific action while they are looking at your marketed product. In general, marketing a website applies the same high-level concept of general marketing practices. Therefore applying AIDA to the structure of your site makes sense. AIDA stands for Attention, Interest, Desire and Action and here is how you can apply it to your website structure:

Attention:
You have an average of four seconds to grab a visitor's attention. The simplest way to do this is by having an attractive headline that can catch the attention of your readers. This does require you to know and understand the audience you are directing yourself to. Read more about Writing for Your Target Audience. You can also apply a concept of attractive graphics and text that are pleasant to the human eye.

Interest:
Build interst with site design and navigation. Include intriguing options that pull people to additonal pages on your website. Again, need to know your audience. I will use this same topic as an example. I know my audience, I know what you (you the one who is reading right now) is looking for, as I explained to you how to catch the attention of your readers, I included further readings on Writing for Your Target Audience. Use the same concept for your website, where you will give your readers the option to expand their knowledge by visiting a related topic within your website.

Another very effective way to gain interst is by giving your visitors or audience something they will find valuable for FREE. And here is another example, most of my visitors are Web masters looking to increase traffice and SEO value, so I give them an opportunity to get a back link to their website for FREE by submitting it to my article directory or link directory.

Desire:
Create a sense of urgency for your visitors to take an action. If you are selling a product that requires shipment, you can include a phrase such as "order today and get free shipping".

Action:
Right from the beginning, make it obvious what you want visitors to do. Whether it is to buy a product online, make a call, inquire by email etc. Then ensure to provide the most ease for visitors to take those actions. For instance, if you want your visitors to subscribe to a newsletter, offer a free eBook on something of their interst and include a subcription form right on the home page.

Websites are not like books, where readers read from front to back. Web visitors may skip around through your pages finding what interests them the most. Not every visitor wants the same thing so you must juggle appeals to multiple subsegments of your target audience.(1). Read more on Inspire action with your Marketing or Sales Copy

Ref: Web Marketing For Dummies