Well, if the data you want to webify is on the other end of: nfs mounts, smb mounts or odbc accessible, (db2, flat files, etc...) you're set, if it's stored in a app like CICS or IDMS, you may need to look at other software, as there isn't a whole lot out there that can talk to those types of apps.
Where I work we use Vega 90 to make idms dialogs appear on a web interface. It's clunky and difficult to program in, but it works, and lets us keep all those bix rules on the mainframe.
We use vega 90 as our interface for PHP, by passing it get urls to get xml and html pages. i.e. fopen("http://mainframe/DIS001S.DIA?record=5345","r");