[blaze4218]

Originally Posted by WolfShade

Put the setInterval after the function.

function bildbyte(){
code
}
setInterval('bildbyte()',5000);

That should read

setInterval( bildbyte , 5000 );

And to address

why doesn't it work?

I would venture:
-either Logic Ali's reply
-or the $() is expecting a string. ie: $('body')