Why some Web sites are much slower than others

John asked why one Web page "comes up right away, while another takes quite a long time to load."

You can't set a clock by your Internet download speed. A great many factors make one page faster than another. And a great many other factors can make the same page fast one day (or hour) and slow the next.

Most of these variables are completely out of your control. But it's still worthwhile to understand them.

[Email your tech questions to answer@pcworld.com or post them on the PCW Answer Line forum.]

First, there's the page itself. Pictures take more time to download than text, and large pictures take more time than small ones.

A well-written page--and I'm talking about code, not text--will take less time to load than a poorly-written one.

And then there's the server. That Web page exists on some computer--a server--somewhere on the Internet. How fast is that server? And how many other pages is it sending out to other people at the same time? Your computer slows down when you're running too many programs. So does a server.

What's more, the Web page probably didn't exist on the server before you requested it. Most pages on the Web are created by a database query. The query speed is another potential bottleneck, especially if you have a slow or overloaded server.

Then the page has to get from that server to you. To do that, it goes through several additional servers, and the cables connecting them. Any one of these could be overloaded or in poor condition.

What can you do about it? Not much. If most pages download quickly, improving your own Internet connection is unlikely to help the slow ones.

But here's one thing you can do. If a page seems to be taking forever, cancel it and try again. And if that fails, try again in an hour.

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