Invalid url?

Trying to get Piwik up and running on my website…

Have run through the install and added the javascript coding before the tag
(this was the resolution to my problem in my previous post)

My Dashboard however is informing me that ‘no analytics data has been tracked’
and urging me to ‘set up javascript tracking on my website and refresh the page’

As far as I can see I have done this and it all seems to be in order.

However… a couple of the lines of the generated javascript are causing me concern viz:

var u="//";

(not sure what the protocol in the forums is so I’ve replaced my website name with ‘mywebsite’)
should the url reference be prefixed with http: ?

It makes no difference if i simply insert http: into the coding and then reload (tried that)
My concern is that when i input the url during setup i didn’t include the http: prefix, so has piwiki used that ‘invalid’ coding elsewhere too?
Am I making sense?