function createImgArray ( len ) { 
  this.length = len;           
    for ( j = 0; j < len; ++j ) 
      this[j] = new Image(); 
  return this;
}

if ( document.images )  {
  topImg = new createImgArray(7);
  ovrImg = new createImgArray(7);

  topImg[0].src = "buttons/dlmc.gif";
  topImg[1].src = "buttons/jmj.gif";
  topImg[2].src = "buttons/sa.gif";
  topImg[3].src = "buttons/aa.gif";
  topImg[4].src = "buttons/bio.gif";
  topImg[5].src = "buttons/links.gif";
  topImg[6].src = "buttons/home.gif";

  ovrImg[0].src = "buttons/dlmc_alt.gif";
  ovrImg[1].src = "buttons/jmj_alt.gif";
  ovrImg[2].src = "buttons/sa_alt.gif";
  ovrImg[3].src = "buttons/aa_alt.gif";
  ovrImg[4].src = "buttons/bio_alt.gif";
  ovrImg[5].src = "buttons/links_alt.gif";
  ovrImg[6].src = "buttons/home_alt.gif";      
}

function swapImg ( index ) { // 'ovr' is the mouseover image
  if ( index == 0 && document.images["doglake"] ) { // doglake
    document.images["doglake"].src = ovrImg[0].src;
  } else if ( index == 1 && document.images["jmj"] ) { // jmj
    document.images["jmj"].src = ovrImg[1].src;
  } else if ( index == 2 && document.images["saahe"] ) { // saahe
    document.images["saahe"].src = ovrImg[2].src;
  } else if ( index == 3 && document.images["aata"] ) {  // aata
    document.images["aata"].src = ovrImg[3].src;
  } else if ( index == 4 && document.images["biog"] ) { // biographies
    document.images["biog"].src = ovrImg[4].src;
  } else if ( index == 5 && document.images["links"] ) { // links
    document.images["links"].src = ovrImg[5].src;
  } else if ( index == 6 && document.images["home"] ) { // home page
    document.images["home"].src = ovrImg[6].src;
  }
}

function restoreImg ( index ) { // 'top' is the original or mouseout image
  if ( index == 0 && document.images["doglake"] ) { // doglake
    document.images["doglake"].src = topImg[0].src;
  } else if ( index == 1 && document.images["jmj"] ) { // jmj
    document.images["jmj"].src = topImg[1].src;
  } else if ( index == 2 && document.images["saahe"] ) { // saahe
    document.images["saahe"].src = topImg[2].src;
  } else if ( index == 3 && document.images["aata"] ) {  // aata
    document.images["aata"].src = topImg[3].src;
  } else if ( index == 4 && document.images["biog"] ) { // biographies
    document.images["biog"].src = topImg[4].src;
  } else if ( index == 5 && document.images["links"] ) { // links
    document.images["links"].src = topImg[5].src;
  } else if ( index == 6 && document.images["home"] ) { // home page
    document.images["home"].src = topImg[6].src;
  }
}