Hi Joan,
Here's mine.
http://www.pbase.com/stuegan/prague
For photos, the area between Wenceleslas Square and the Charles Bridge is very picturesque, and there are plenty of interesting things to see round there, not least on the Bridge itself. It's generally known as the Old Town and it's a great place to lose yourself in the winding streets. Josefov, the area north of the Old Town is also well worth a look.
The New Town (basically south/south east of Wenceleslas Square I think) is worth a look too, though not quite as picturesque. Some interesting buildings round that way, but then the architecture throughout Prague is magnificent and most newer buildings seem to have been designed so that they don't take the attention away from the older ones.
My favourite part though was Malostranska/Mala Strana, which is the area on one side of the Charles Bridge that leads up to the castle. Full of narrow, winding streets, very colourful, and it feels like there's a bit more normal daily life going on here amongst all the tourism.
Last, but not least, the area between the river side and the Furnicular in Petrin Park brings up some interesting sights if you wander aimlessly!
You'll definitely manage to see most of the city centre in 4 days though - it's quite easy to walk around. The areas I've mentioned are definitely just the main 'tourist' areas though - I think a resident of the city might be able to suggest some lesser known gems!