UsefulConcept

Norton personal firewall has an ad blocker which filters out ads from web sites. This feature is turned on by default for the 2004 version, but reportedly has to be manually turned on for current versions.

The way the software works is that it looks at the image name, size and path and though some filters it will either allow it to be shown or not.

what this means is that a perfectly legitimate image (logo, photo, etc) can be filtered out if you name it or size it to something norton doesn't like.

Here are some examples of bad names/sizes:

125x125 160x600 180x150 234x60 240x400 250x250 300x250 336x280 468x60 88x31 120x90 120x60 120x240 /banner/ /banner. &banner= /banner= bannerad banner_ad /bannerads/ /banner-ads/

The full list I found goes on for a very long time. I have no idea if the whole list is accurate or complete, but I DO know that 250x250 is in fact filtered out.

We released a site recently that has logos and photos in the member area sized at 250x250. So many users were complaining that their images were not showing up. The quick fix was to change the HTML to be 249x249. Thats right. Norton doesn't check the image, but rather the html.

Another way to trigger this is to use an htaccess file configured to not show images without an http referrer being from your own site (so others don't steal your bandwidth showing your images on their site). Well Norton and other tools will often not report the referrer.

While I understand why people may want those filters, I find it infuriating that it is done so poorly. So double check your sizes and remember if you make any images make them in odd numbered height or width. Don't put them in a /banner/ folder, etc.

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