I am trying to cache a site and do not want to download thumbnail images.  I
attempted to achieve this by using the below scan rule filters.  I am still
getting the thousands on thumbnails.  Is there something wrong in my filter?
The site I am caching is uses php.  A PHP command is calling the images. 
Could that cause the filter to not apply?
+*.css +*.js -ad.doubleclick.net/* -mime:application/foobar
+mime:text/html
-*.gif*
+*.gif*[< 21]
-*.jpg* 
+*.jpg*[< 21]
-*.png*
+*.png*[< 21] 
-*.tif*
+*.tif*[< 21] 
-*.bmp*
+*.bmp*[< 21]