I can't upgrade iWeb like before . Why ?

Do you mean upgrade - to get a new version of iWeb? Or do you mean 'upload' - publish changes to your website?

iWeb is no longer sold by Apple unless you can find a copy of the iLife box, and online updates are not available.

You cannot upload your website to MobileMe as it is now closed: you will need to find another hosting service and upload your site from iWeb to that - please see this page for more information.

http://rfwilmut.net/missing2

iWeb V 3 has two other options for publishing...

http://www.iwebformusicians.com/iWeb/Publish-Website.html

... and there's lots of hosting to choose from...

http://www.iwebformusicians.com/iWeb/Website-Hosting.html

The Mobileme only features can be replaced with other options...

http://www.iwebformusicians.com/iWeb/Comments-Password-Protect.html

If/when you upgrade your OS to Mountain Lion, see this page...

http://www.iwebformusicians.com/iWeb/mountain-lion.html