When creating web designs, you really have to be on point. Learn more about what is important, including the right frame of mind. You will also find that the advice about web design included here is simple to follow.
If you're designing a website, make sure the code you write has a valid HTML+CSS. Although most browsers can make sense of code that isn't valid, it could be rendered correctly or incorrectly. Valid code will render the same way most of the time in modern browsers. You can check the validity of your HTML code with an HTML validator.
Make sure your text and background has the proper contrast. There's evidence showing that white text on a black background is easiest for most people to read, but other colors are fine so long as they're readable. Also keep in mind that people with visual impairments may not be able to read your site if the contrast is poor. Check to see if your site complies with various contrast standards using the tool at http://snook.ca/technical/colour_contrast/colour.html .
When you are creating graphics or photos for your website, be sure to keep the file size small. If your graphics are too large, your page will load slowly and your visitors will leave. You can find many free or inexpensive graphics programs online that will optimize your images before you load them to your website.
For multimedia presentations, take advantage of the new HTML5 standard. Although HTML5 isn't quite as robust for animation and games as Flash, it has the advantage of working stably on mobile phone browsers, including those contained in Apple hardware. HTML5 is also quite a bit leaner than Flash, so load times will improve, as well.
In summary, there are many valid reasons for knowing how to best design a website, and how important it is to know how to do it. Remember that the great tips here will help you to come up with ways to do better at your site design so things work out well for you.