GZip Compression being blocked by firewalls

[alesmith]

I was speed optimizing a OSC site for a customer and decided to enable the GZip compression from the Configuration menu. I set it to true with compression level set to 5.

Everything fine at my end I could see the the site and basic functional tests showed nothing was broken.

 

My client then called to say he could not see the site and VISTA diagnostics reported content had been blocked by a security policy.

 

Has anyone else had similar experiences with GZip compression?

 

My security is an SPI/NAT firewall on my netgear router and Norton on each of my XP PC's with XP firewall disabled.

My client's security is SPI/NAT on a netgear router and AVG on a Vista PC (with Vista firewall disabled).