Here is the simple tip to know whether the current web page offers RSS subscription or not, with this method you can subscribe to specific RSS (if available).
Step 1: Open Mozilla Firefox’s Toolbar Layout ( Firefox > Options > Toolbar Layout… ).
Step 2: Drag Subscribe icon to Bookmark Toolbar.
So, next time you see the ‘Subscribe’ button active, it means RSS feed is available for the particular webpage.
Here the subscribe button asks me specifically select the RSS service to be subscribed.