creating my own RSS feed 2.0

<rss xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:taxo="http://purl.org/rss/1.0/modules/taxonomy/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" version="2.0">

I noticed that the rss tag allows for xml name spaces so does this mean I can create an rss feed with tags other than the tags defined within the rss spec?

For example say I was 开发者_开发技巧a online store who wanted to use rss to advertise new products. I could define a tag for the price of the product.

Yes, but bear in mind that adding other namespaces to your XML does not mean that downstream software will automatically be able to make use of the tags. If you add the price of your product to your XML, it won't necessarily be parsed meaningfully by RSS consumers. It shouldn't blow them up either, though.