hi, i am a beginner in the servlet world and i can tell you this much : lots, and the errors are more difficult to figure out than simple java programs.
There can be many sources of errors : web.xml, jsp, servlet, listener etc. The challenge i encountered : To make them all work in unision.
One such problem i am currently facing : bugged Try developing some servlets, jsp's of your own and you will see the problems.
Do you have any certifications, self-made projects etc ?
BTW, i have not yet seen any companies that give development jobs to freshers. They ask for experience and knowledge of multiple technologies.