Edit wordpress website directly on domain or offline then upload ?

Hi

Just started to finally use wordpress and the enfold theme to build my own website. When I initially looked at this, I created my wordpress website offline, setup php, sql etc. all offline, then uploaded the relevant pages etc to my domain. With my hosting company there was an option to install wordpress using their simple scripts, which then allowed you to edit the website directly via the domain/wp-admin. I did this and then decided to import the dummy data and create my own pages from these, then I discovered that all the dummy data pages were being indexed by Google which I did not want, I therefore deleted the dummy data and only kept the pages I had created, unfortunately any page that does not exist by someone typing non existent URL’s, now brings up the enfold theme headers etc. I don’t have a 404 page.

Is there a better way to do all this, I’m guessing the offline mode would give a more in control feeling ?

many thanks for any help
Kevin