I have created custom option like Age group at the time of add a product. Now i want this custom option as filterable in left navigation of category page. Can any one help me how can i do this?
It depends what type of attribute it is but if you edit the attribute through the admin area, if available there will be options to allow in layered navigation.
Catalog > Attributes > Manage Attributes
Sorry i misunderstood. It is not possible to add custom options to the layered navigation. One solution, albeit a bit messy, would be to create the custom options as attributes as well and have the same values in there. That does double up on the work you would have to do to create a product though so you could take it further and have a custom module that creates and updates attributes automatically based on the custom option choices.
Hope that helps a little more than my previous reply
Thanks once again! I got your point. but I am a new to magento. so can you provide the code snipet or more explaination to do this ?