This market is sufficiently in the doldrums that I'm not sure pursuing certification is going to up the odds of being hired or getting promoted in this field. My advice would be to continue to hone your technical skills and abilities, and to develop as impressive a portfolio of sample sites, applications, tools, and so forth as you can to show current and prospective employers what you know and what kinds of things you can get done.
Although certification seems like a natural fit for Web technologies given how technical and broad the field can be, Web technologies change so quickly and include such an interesting mix of proprietary and standard bits and pieces that no Web certifications have really taken off in really big numbers nor have the vendors or sponsors behind such programs been able to create sizable certified populations and/or realize commercial success.
HTH, and good luck with your future career efforts and planning. Feel free to post again if you have further comments or questions.
This was first published in May 2003