The short answer to that is basically NO. iWeb never has been available for download except for updates and also iWeb was discontinued by Apple at least 2 years ago, once MobileMe went and was replaced with iCloud, that did not offer a hosting facility.
If you don't have iWeb and you want to use it then you'll either need to install it from the installation CD's that came with your wife's computer or you need to go and buy a copy of either iLife 09 or iLife 11 from Amazon and install it from there. I would think you will probably need to purchase a copy of iLife from Amazon, depending on how old your wife's Mac is? It could be that she had iWeb 08 on her Mac which will not work with Mavericks if you have a new Mac, so you will need to buy a new copy of iWeb 09 via Amazon on iLife 09 or 11 for it to work with Mavericks.
As iWeb is no longer sold or supported by Apple and has not been for the last 2 years, why not try new software to re-create your website? There are lots out there to look at - RapidWeaver, Sandvox, Freeway Pro/Express 6, WebAcappella 4, Flux 4, Macaw and EverWeb - this is the most like iWeb and can be found at http://www.everwebapp.com. You should be able to download free trials of all of these so that you can try before you buy.