no suitable driver

hi, i've this typical error, i've read some stuff about it but many concern applets, and my problem comes from a jsp
page.

i've the jar of distribution load from TOMCAT in it lib directory.

before that i've the 'unable to load class...' Now that i pt the jar in tomcat/lib nad modify the script to generate a
goodclasspath value i've the "no suitable driver" 

My configuration is APACHE 1.3.20/WIN NT 4.0 SP 4/TOMCAt 3.2/POSTGRESQL 7.1.2

Thank for help !

Matthieu