I don't understand your setup myself...but I can offer a *little* bit here.
Localhost is *very* different from regular internet traffic. A locahost server is a *private* server that resides on your home computer. You can have your setup on your home computer with MySQL, PHP, Apache - all the goodies - just like you would get from your own hosting provider. However it's kep private because it resides on your own hard drive, and the only way to access it is through a local IP address - usually 192.168.1.1 (or something similar). 192.168.x.x IP addresses are reserved solely for the purposes of private access - meaning it's the IP address of your computer, whether or not you are actually connected to the outside world through the internet. If you are actually logged into the internet and open your browser window and type in "localhost" or a "192.168.x.x" IP address, it'll look *on your own hard drive* for the server - it will not look to outside access. That's what that IP is reserved for.
Your stylesheets and files are pointing to "localhost". So when you upload the files, etc. to the hosting space that actually is accessed via a regular IP address served up by your host, then you need to have them show the file paths to that server. If you have it via localhost, the internet will not know where to look, because such an IP doesn't exist publicly.
You may have a localhost setup on your home computer. I do, myself. I have an installation of WordPress running on my hard drive, and it's used for testing out my site designs before I put them on a live site. When I *do* put them on a live site, I make sure all instnaces of "localhost" are changed to the proper path for the server it resides on - which is no longer my own when it's made live.
The URL "www.jedeboer.nl" does not live on your home computer. According to whois, it lives with the host of "firstfind.nl" - which means firstfind.nl is your regular web host, and that's what's serving up your live site to the rest of the world.
Trying to enter a post on your localhost computer and hoping it shows up on your live site is like writing a letter on a piece of paper, setting it on the table, and then wondering why the letter never got to your mother two weeks later. They aren't even in the same area to have access to one another.
When you do posts from your home on your PC, or whether you do them from an internet cafe when you travel, you will log into your blog's admin area - the one that lives on your hosts' site. The posts will appear on your live site - but not your localhost. They are not connected together.
Unless I'm missing something, and *you* are "firstfind.nl", and the hosting service is run from your own office (and if so, then I don't know what to tell you because I've never run my own hosting server) - then the two do not connect to one another. You can use your localhost environment for development purposes - but if you want stuff to appear on your live site, them you *must* move everything to the externally hosted server.
I hope that made some sense!