The web Shield is the avast provider in the Home version most similar to the script blocker, that can detect malicious scripts, but I don't think it works in the same way as the Pro versions Script Blocking provider. It is probably less important than it was before the Web Shield provider was introduced, there is also limited browser support for it.
If you are looking at this with a view to getting the pro version, there are other elements that many be better suited to how you want to use avast. The Pro version isn't limited to interactive input requirements of the home version and is more configurable and flexible, see link below.
Avast Home V Avast Pro differences
http://www.avast.com/eng/av4_version_comp.html
