Ok, I set my mapfile like this:
EXTENT 10.6661 59.9155 10.6824 59.9214
PROJECTION
"+proj=eqc +lat_ts=60 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84"
END
and this is what I have had before:
EXTENT 10.6661 59.9155 10.6824 59.9214
PROJECTION
"init=EPSG:4326"
END