However once there is enough navigation links on the page, it is not necessary to split the page into more pages.
I disagree. Even if you provide enough anchors and links, using a single page for all of your content will often overwhelm a visitor, giving them the impression that it is going to take forever to read through your content. Many people are turned off by the thought of reading a web page that goes on and on and on.
Splitting the site up into pages gives a more logical, intuitive feel for users to take in information at a pace that they set. Visitors will be much more inclined to read a page if, upon seeing the page, they know that they can actually finish reading the content in front of them in a timely manner.
what makes you to get bored when the information is located on the same page?
When I click on one of your buttons, let's say Contact, for example, I am taken to that portion of the page. However, now I want to look at a different part of your site. To get to another page, I have to click Back To Top, and
then click the button I want. This extra step will turn off a lot of visitors who are expecting to always have a menu easily accessible.
Alright, on to some of the things I've noticed:
You use some boxes to hold content on your site, but they contain no padding and look somewhat incomplete in a way. For example, the paragraph that starts with "Accessibility can be thought of as "providing..." is in such a box. Some padding around the edges would make it look much better.
The purple boxes don't seem to fit in with the rest of the colors.
I also agree with righteous_trespasser about the buttons, they look too outdated, too early 90's-ish.
For your color scheme, I can see how you're basing it around the header image, but the red, orange, green, blue, purple, it's all just too much going on and makes the site seem a little disorganized. Try narrowing your colors down to two or three and stick with them throughout the site. For example, the blue text on orange background for your section headers does not blend well.
Finally, the background color just seems a bit off in my opinion. I can't quite put my finger on it, but the creme color just seems too dull. Try playing around with a background that's a bit brighter.