where do i download iweb from?

iWeb.app isn't available for download. In fact it isn't available from Apple anymore.

If you want a copy you need to look online for the old iLife Disk.

To get a copy of iWeb 3 (and iDVD 7 which is also discontinued) you'll need to purchase a copy of the boxed iLife 09 or 11 disc from one of the 3rd party retailers like Amazon.com: iLife 11

OT

Can I install only iWeb or iDVD? Does it create any conflict with the actual iLife?

You can install single applications from the disc as you want to and there should be no conflict.

If you want to you can install just iWeb or iDVD or both with no problem.

When you get to Installation Type: Click on the customize button at the bottom

Here the installation will allow you to choose which applications to install.

Select iWeb & click install. (iDVD can be installed at this point if you want. In that case you would select iWeb & iDVD then click install)

After the install is complete run “Software Update” from the apple menu or the app store. There will be some updates for iWeb/iDVD to allow them to work with the other iLife apps

You can copy it from an another mac, and then run the update you dowloaded from the Apple site. It worked for me with Mountain Lion...

Thas't really clever! Which file did you copy and where is it?

The Application it self can be copied to the new machine

I just stumbled upon this recently:

You will still need the iWeb "Domain" file. That is what actually has your website information "files"