Nerval's Lobster writes: Having one or more certifications sounds pretty sensible in today's world, doesn't it? Many jobs demand proof that you've mastered a particular technology. But is the argument for spending lots of time and money to earn a certification as ironclad as it seems? In a new column, developer David Bolton argues 'no.' Most certifications just prove you can pass tests, he argues, not mastery of a particular language or platform; and given the speed at which technology evolves, most are at risk of becoming quickly outdated. Plus they aren't the sole determiner of whether you can actually land a job: 'Recruiters sometimes have trouble determining a developer's degree of technical experience, and so insist upon certificates or tests to judge abilities. If you manage to get past them to the job interview, the interviewer (provided they're also a developer) can usually get a good feel for your actual programming ability and whether you'll fit well with the group.' Are certifications mostly a rip-off, or are some (especially the advanced ones) actually useful, as many people insist?