Keep It (the graphic and visual web elements) Simple and give the eye Space.
Nothing ruins a website faster than bad graphics. There is a real art to creating graphics for the web. Images need to download quickly, yet maintain image quality. When placing graphics/visuals on your webpage leave sufficient white space (don't throw everything + the kitchen sink of clip art on your page.). Too little white space and your page can feel cramped and constricted. Too much white space and things look as if you don't have much to say... Simple is not simplistic, simple is the masterful balance of just enough information to inform and yet over whelm.
Remember, the eye needs space to make good decisions. White space is prime space. "White space" doesn't have to be white, but it does need space. Soft, neutral background colors like light grays and beiges work well too. Even simple graphic patterns such as fades and light stripes work. The idea is to create a stylish, yet simple canvas for your message. Strong colors and contrast draw the eye to the important points on a page. Use these points and color sparingly.
Usually keep your text to one dark color. You may use a highlight color for subheads or headlines, but just because your computer allows text in 1000s of colors should not be the reason to use it. Many readers find reading a computer screen tiring, so avoid yellow and fluorescent text, it is difficult to read on screen. No more than three colors, please, that's enough. Too much color looks amateurish-with all the competition on the web it is important to look professional and up-to-date.
Another way to keep the visual simple is to limit the number of fonts.
As with colors and graphics, you can have font variation without confusion. Limit the number of fonts and font styles you use. Just like with color, try to use no more than three fonts.
Make sure the body copy is legible (test the size in all browsers on both the Mac and PC). Consider your audience, the older the target audience the larger the type and the darker the color. If your target market is older than 40, consider using bigger text (14 point) to help the quick "scanability" of your page. Use reverse type sparingly, especially if your target market is older than 55.
Most people just scan a page; they don't really read it from top to bottom. Fewer distractions with fancy fonts increase the ability to scan a page quickly. Studies show they read the headline and the p.s. first, and then read the subheads and bullets. Bullets increase the scanability factor of a page for all ages yet, search engines don't really like bullets, so just like with colors, and fonts, balance is key.