You are not aware.
You download a webpage every time you visit it. Web apps and downloads do belong in the same sentence.
I am not "aware"? Yes, technically speaking, a web page is 'downloaded' when you view it. But when referring to web apps, nobody ever uses the term "download", you use "download" when referring to native run apps.
For example:
I installed Microsoft Office (from a CD)
I downloaded OpenOffice.org (from their website,)
I run Google Apps (from their website.)
I do not "download" Google Apps in the same manner that I "download" OpenOffice.org