For completeness here is another writeup of the integration of Liferea with different browsers:
If you using Epiphany you only need to enable the feed subscription plugin which is delivered per default (in some distributions as a epiphany-plugins package). To do so enable the "News Feed Subscription" extensions under Tools/Extensions. If the plugin is enabled and the currently loaded website provides a feed you will see an icon in the toolbar as shown in this screenshot on the left.
After clicking the icon the subscription will be added.
If you are using Firefox 1.5 you need the FeedBag extension. You can download it from the Liferea Homepage or from the Mozilla Addons website.
When using Firefox feeds are represented by the orange feed icon in the URL bar. To subscribe to a feed just click the icon. In the default setting clicking the icon will add the feed to the Live Bookmarks of Firefox. If you want to directly add a subscription to your feed reader you need to change the subscription preferences. This can be done under Tools/Edit Preferences in the "Feed" tab. For Liferea you need to specify the command "liferea-add-feed" as shown in the screenshot below:
The "liferea-add-feed" script should come with your Liferea package and uses DBUS to send a subscription request to the running Liferea instance.