Perhaps you could keep a record of the line number that you're currently displaying and create previous and next buttons which set a CGI parameter for the previous and next lines. You CGI script could then read through the file using $. to check when it's on the right line and display the data found on that line.

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<http://www.dave.org.uk>

European Perl Conference - Sept 22/24 2000
<http://www.yapc.org/Europe/>