Webhoster inserts a javascript which brokes my code how to remove it?

They have a link in their cPanel where you can disable the analytics code.

http://members.000webhost.com/analytics.php

EDIT

Beware - by doing this you violate their policy and they will eventually drop you from their service and you will lose all your data.

In case anyone run into this problem in the future, to stop the analytic code from being included, all you have to do is use the exit() command at the end of your script. The code is in a PHP auto-append file. It doesn't get executed if you exit explicitly instead of letting the script reach the end of the file. The setup at 000webhost.com parses HTML through PHP as well. If you want your regular HTML files to pass validation, add at the very end the following:

<?php exit; ?>

Adding to Catfish's answer,

They have a link in their cPanel where you can disable the analytics code.

http://members.000webhost.com/analytics.php

EDIT

Beware - by doing this you violate their policy and they will eventually drop you from their service and you will lose all your data.

As asked by asalamon74 in the comments,

When I disable the analytics code with this method my domain get canceled due to inactivity. Is there a way to avoid it

Yes, there is a simple way to avoid it. Go ahead and enable your analytics code. Visit http://members.000webhost.com/analytics.php and enable it again.

Then, create a .htaccess in your public_html folder and add the following code to it:

<FilesMatch "\.(php)$">
php_value auto_append_file none
</FilesMatch>

This will prevent all .php files from been appended with the analytics code. Just replace php with any file extension where you want the analytics code removed.

That's all. This way your domain won't get cancelled. Hope it helps.