Thanks for the reply. Why should I think that you're a 'complete Dumbo'? I knew nothing about digital photo frames until I bought my son and his wife one last Christmas ;-)
The frames normally don't come with memory cards. (Many people already have a few spare cards for their camera, so not everybody needs another one for the frame). It probably makes most sense to buy the same type of card that your camera uses (e.g. SD, XD, MMC, etc) but, as I stated before, most frames (and card readers) will accept any of the common types of card.
The number of photos you can store on the card will depend on the file sizes and the capacity of the card. If you want to store a lot of pictures, it might be worth reducing the file sizes by using the software which came with your camera. Alternatively, use the Image>Resize/Resample facility in Irfanview:
http://www.irfanview.com/
The capacity of the card will determine its price but High Street prices are often much dearer than web purchases. For example, the cheapest 1Gb card in the current Argos catalogue is priced at �17.99. eBuyer will sell you one for �3.29:
http://www.ebuyer.com/product/83430
Chris