Career Shift: M/F to Web – How?

I am considering returning to work after a 1.5-year hiatus. I would like to shift my career focus from mainframe-based to web-based.

My career history looks like this:
2000-present: unemployed
1997-1999: print application development in IBM mainframe environment
1997-1996: C programmer
1995-1996: Access 2.0 developer
Certifications: Computer Systems Diploma

What do I need to do to become an employable commodity in the Web Development or PC Software Development arena?