//preload images first
img1=new Image()
img1.src="images/but_about_up.gif"
img2=new Image()
img2.src="images/but_about_over.gif"
img3=new Image()
img3.src="images/but_about_down.gif"
img4=new Image()
img4.src="images/but_practice_up.gif"
img5=new Image()
img5.src="images/but_practice_over.gif"
img6=new Image()
img6.src="images/but_practice_down.gif"
img7=new Image()
img7.src="images/but_firmprof_up.gif"
img8=new Image()
img8.src="images/but_firmprof_over.gif"
img9=new Image()
img9.src="images/but_firmprof_down.gif"
img10=new Image()
img10.src="images/but_directions_up.gif"
img11=new Image()
img11.src="images/but_directions_over.gif"
img12=new Image()
img12.src="images/but_directions_down.gif"
img13=new Image()
img13.src="images/but_contact_up.gif"
img14=new Image()
img14.src="images/but_contact_over.gif"
img15=new Image()
img15.src="images/but_contact_down.gif"