What is eight second rule?

This rule implies that the internet user only waits eight seconds for a web page to download or appear, if it takes more than 8 seconds the internet user will leave the page and go to another website.

So companies and webmasters are advised to put their pages of a website simple so that they appear in  less than eight seconds.

ps. Do not use the flash animation even though it looks good, because it slows the download time