No, it is not available on the app store. You would have to obtain an older version of iLife to get iWeb. Check out Amazon if you really want it. Honestly, even though I really loved iWeb for its simplicity, you should probably go with something more modern. There are several apps out there that basically take the place of iWeb and you could also easily learn WordPress. At least with WordPress you're not tied to a platform and can even do updates from mobile devices.
Apple Iweb For Mac
Edit:
For a direct replacement to the iWeb app you might look at these:
http://www.karelia.com/products/sandvox/
http://www.everwebapp.com/
Apple Iweb For Mac Shortcut
Apple Iweb
Or if you don't feel like messing with WordPress and want something that isn't tied to the Mac platform you could get the basic equivalent from services like these:
http://www.squarespace.com/
http://www.wix.com/
Apple Iweb For Mac Windows 10
Read reviews, compare customer ratings, see screenshots, and learn more about iWeb SMS. Download iWeb SMS and enjoy it on your iPhone, iPad, and iPod touch. Write your text messages on the Mac or PC in your favorite browser with a real keyboard. It gives me creative possibilities with my Mac that don't exist elsewhere, and it follows the 'Mac/Apple' personality of user-friendly. I cannot express what that means in benefits. If you're a Mac/Apple person, this is the best choice for developing and maintaining your own creative website — no matter the style. IWeb 09 is Apple's Web site design and publishing tool. With it you can lay out your Web site without knowing HTML or CSS, apply preconfigured themes,. Create gorgeous documents in minutes with the Pages for Mac word processor. Start with an Apple-designed template to instantly create gorgeous reports, digital books, resumes, posters and more. Or use a blank document and create your own design. Easily add images, movies, audio, charts and shapes.