There are best DJ softwares to mix songs like pro DJs. But just for fun, If you like to try out some djing skills online, then you can do so with YouTube videos and a **** crossfader which controls the volume of the left and right panes or videos in this case.
How to Remix Two YouTube Videos Online
> Go to "Two YouTube Videos and a Motherfucking Crossfader . Com" : Link
God knows why the url is so long and strange; But in case you didn’t get it from the domain name, the web site basically presents you with two YouTube videos. And a crossfader. (Also Some Really Funny Domain Names)
But it works Great.