How To Validate URL And Keywords

I want to validate an imdb URL and an keywords field who contain minimum 3 words separated by comma. This script valdate any url, but I want to validate url like this: [uRL]
var urlRegex = /http://[A-Za-z0-9.-]{3,}.[A-Za-z]{3}/;
if(url == "") {
inlineMsg('url','<strong>Error</strong><br />You must enter an URL.',2);
return false;
} if(!url.match(urlRegex)) {
inlineMsg('url','<strong>Error</strong><br />You have entered an invalid url.',2);
return false;
}