User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; rv:1.7.3) Gecko/20040913 Firefox/0.10.1 Build Identifier: Mozilla Thunderbird 0.9 (Windows/20041103) Thunderbird downloads all of feeds whether or not it is modified since last download. If HTTP request includes "If-Modified-Since" header, the server may return "304 Not Modified" response with no contents. This can save traffic and time of download. Reproducible: Always Steps to Reproduce:
Created attachment 181213 [details] [diff] [review] the fix 1) After downloading a feed, we now look for a "Last-Modified" response header from the server. If we find one, we remember it as an RDF property on the feed. 2) Before downloading a feed, we look for a stored Last-Modified header in the data source. If we find one, we set a "If-Modified-Since" request header before opening the request. 3) Handle Not Modified responsese from the server and show an appropriate message in the status bar instead of treating it like an error.