iCloud doesn't have the facility for hosting websites.
You would need to get a hosting account...
... and publish your website using one of the methods show here...
iCloud does NOT allow you to host your web sites. You can continue to use iWeb but, will need a 3rd party web host to upload your websites to. Depending on the version of iWeb you are using you have a couple of publishing options:
iWeb '09 (3.0.4) you can publish to an FTP Server or a local folder. ( With the built in FTP in iWeb you will end up with an address like "www.YourDomain.com/sitename/Home.html )
iWeb '08 you can publish your website to a local folder
I have been using IX Webhosting for several years with little to no problems "usually the problem was something I did" and they have been quick to solve any issue I have come across. The have plans that start at $3.95 a mo (USD) and their customer service is top notch.
"I may receive some form of compensation from my recommendation or link."
Here is a video tutorial that will explain the entire process of moving your website from MobileMe to a web host. I highly recommend the hosting service as well.