If you don't want your clients to see a proxy (I assume that what you mean
by transparent) don't you need to filter outgoing port 80 tcp and NOT 8080
tcp???

Just a minor point... (I might be wrong)

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Psychogios, Dimitrios K.
QUALCO Business Systems Design & Implementation
IT Services Division
www.qualco.biz
Voice: +30 210 6198903 Ext: 207
Fax: +30 210 6178140
mailto:dpsychogios at qualco dot gr