One of the problems with designing websites is that there so many internet browsers available, it is really hard to make sure that your site looks the same in all of them. Generally, if your site is well-designed, it should at least “work” in most of them, but even that is not guaranteed. I usually try to test my websites in whatever version of Firefox, Internet Explorer, Netscape, and Opera I have on my computer (which is usually the latest version), but even that is not enough, because there are a lot of people out there who don’t bother (or don’t know how) to upgrade their browsers, people who use different operating systems (Mac, Linux, or even different iterations of Windows), and people whose computers just don’t have enough juice to run some of the fancy-schmancy websites out there.
Unless you have a team of people with an array of computers with various operating systems and browsers, it can be rather difficult to test your website under a variety of conditions. One site that helps to make your life (as an amateur web designer) easier is Browser Shots. If you enter your website’s URL into the box at the top of the page, the site will create an image of your site in the various browsers and operating systems that you choose in the section below the box. It can take a while for the images to be formed, so you can go and browse other sites (in the same browser, if you have tabbed browsing — and if you don’t have tabbed browsing, you should — or in a separate browser that you open).
Screenshots of this site. Notice how the video doesn’t
show up in some of them. That’s because the code that the
sites give you to embed their videos isn’t always coded nicely.
Doing this still doesn’t guarantee that your site will work on every single computer in the world, but it will certainly get you closer to that goal.