img1_off     = new Image(41,41)
img1_off.src = "images/off_home.gif"
img2_off     = new Image(41,45)
img2_off.src = "images/off_login.gif"
img3_off     = new Image(41,45)
img3_off.src = "images/off_demo.gif"
img4_off     = new Image(41,45)
img4_off.src = "images/off_try.gif"
img5_off     = new Image(41,45)
img5_off.src = "images/off_join.gif"

img1_off_over     = new Image(41,41)
img1_off_over.src = "images/off_over_home.gif"
img2_off_over     = new Image(41,45)
img2_off_over.src = "images/off_over_login.gif"
img3_off_over     = new Image(41,45)
img3_off_over.src = "images/off_over_demo.gif"
img4_off_over     = new Image(41,45)
img4_off_over.src = "images/off_over_try.gif"
img5_off_over     = new Image(41,45)
img5_off_over.src = "images/off_over_join.gif"

function rollOver(imgID,state) {
  document.images[imgID].src = eval(imgID + "_" + state + ".src")
}