function BrowserDetect() {
   var ua = navigator.userAgent.toLowerCase();

   // browser engine name
   this.isGecko       = (ua.indexOf('gecko') != -1 && ua.indexOf('safari') == -1);
   this.isAppleWebKit = (ua.indexOf('applewebkit') != -1);

   // browser name
   this.isKonqueror   = (ua.indexOf('konqueror') != -1);
   this.isSafari      = (ua.indexOf('safari') != - 1);
   this.isOmniweb     = (ua.indexOf('omniweb') != - 1);
   this.isOpera       = (ua.indexOf('opera') != -1);
   this.isIcab        = (ua.indexOf('icab') != -1);
   this.isAol         = (ua.indexOf('aol') != -1);
   this.isIE          = (ua.indexOf('msie') != -1 && !this.isOpera && (ua.indexOf('webtv') == -1) );
   this.isMozilla     = (this.isGecko && ua.indexOf('gecko/') + 14 == ua.length);
   this.isFirebird    = (ua.indexOf('firebird/') != -1);
   this.isNS          = ( (this.isGecko) ? (ua.indexOf('netscape') != -1) : ( (ua.indexOf('mozilla') != -1) && !this.isOpera && !this.isSafari && (ua.indexOf('spoofer') == -1) && (ua.indexOf('compatible') == -1) && (ua.indexOf('webtv') == -1) && (ua.indexOf('hotjava') == -1) ) );

   // spoofing and compatible browsers
   this.isIECompatible = ( (ua.indexOf('msie') != -1) && !this.isIE);
   this.isNSCompatible = ( (ua.indexOf('mozilla') != -1) && !this.isNS && !this.isMozilla);

   // rendering engine versions
   this.geckoVersion = ( (this.isGecko) ? ua.substring( (ua.lastIndexOf('gecko/') + 6), (ua.lastIndexOf('gecko/') + 14) ) : -1 );
   this.equivalentMozilla = ( (this.isGecko) ? parseFloat( ua.substring( ua.indexOf('rv:') + 3 ) ) : -1 );
   this.appleWebKitVersion = ( (this.isAppleWebKit) ? parseFloat( ua.substring( ua.indexOf('applewebkit/') + 12) ) : -1 );

   // browser version
   this.versionMinor = parseFloat(navigator.appVersion);

   // correct version number
   if (this.isGecko && !this.isMozilla) {
      this.versionMinor = parseFloat( ua.substring( ua.indexOf('/', ua.indexOf('gecko/') + 6) + 1 ) );
   }
   else if (this.isMozilla) {
      this.versionMinor = parseFloat( ua.substring( ua.indexOf('rv:') + 3 ) );
   }
   else if (this.isIE && this.versionMinor >= 4) {
      this.versionMinor = parseFloat( ua.substring( ua.indexOf('msie ') + 5 ) );
   }
   else if (this.isKonqueror) {
      this.versionMinor = parseFloat( ua.substring( ua.indexOf('konqueror/') + 10 ) );
   }
   else if (this.isSafari) {
      this.versionMinor = parseFloat( ua.substring( ua.lastIndexOf('safari/') + 7 ) );
   }
   else if (this.isOmniweb) {
      this.versionMinor = parseFloat( ua.substring( ua.lastIndexOf('omniweb/') + 8 ) );
   }
   else if (this.isOpera) {
      this.versionMinor = parseFloat( ua.substring( ua.indexOf('opera') + 6 ) );
   }
   else if (this.isIcab) {
      this.versionMinor = parseFloat( ua.substring( ua.indexOf('icab') + 5 ) );
   }

   this.versionMajor = parseInt(this.versionMinor);

   // dom support
   this.isDOM1 = (document.getElementById);
   this.isDOM2Event = (document.addEventListener && document.removeEventListener);

   // css compatibility mode
   this.mode = document.compatMode ? document.compatMode : 'BackCompat';

   // platform
   this.isWin    = (ua.indexOf('win') != -1);
   this.isWin32  = (this.isWin && ( ua.indexOf('95') != -1 || ua.indexOf('98') != -1 || ua.indexOf('nt') != -1 || ua.indexOf('win32') != -1 || ua.indexOf('32bit') != -1 || ua.indexOf('xp') != -1) );
   this.isMac    = (ua.indexOf('mac') != -1);
   this.isUnix   = (ua.indexOf('unix') != -1 || ua.indexOf('sunos') != -1 || ua.indexOf('bsd') != -1 || ua.indexOf('x11') != -1)
   this.isLinux  = (ua.indexOf('linux') != -1);

   // specific browser shortcuts
   this.isNS4x = (this.isNS && this.versionMajor == 4);
   this.isNS40x = (this.isNS4x && this.versionMinor < 4.5);
   this.isNS47x = (this.isNS4x && this.versionMinor >= 4.7);
   this.isNS4up = (this.isNS && this.versionMinor >= 4);
   this.isNS6x = (this.isNS && this.versionMajor == 6);
   this.isNS6up = (this.isNS && this.versionMajor >= 6);
   this.isNS7x = (this.isNS && this.versionMajor == 7);
   this.isNS7up = (this.isNS && this.versionMajor >= 7);

   this.isIE4x = (this.isIE && this.versionMajor == 4);
   this.isIE4up = (this.isIE && this.versionMajor >= 4);
   this.isIE5x = (this.isIE && this.versionMajor == 5);
   this.isIE55 = (this.isIE && this.versionMinor == 5.5);
   this.isIE5up = (this.isIE && this.versionMajor >= 5);
   this.isIE6x = (this.isIE && this.versionMajor == 6);
   this.isIE6up = (this.isIE && this.versionMajor >= 6);

   this.isIE4xMac = (this.isIE4x && this.isMac);

   } //end BrowserDetect()

   var detectBrowser = new BrowserDetect();

function setFilterOptions(program){
 var select_elem = document.getElementById('filter_select');
 if (program == 'blastn'){
    select_elem.options.length = 0;
    var opt_none = new Option("none", "none", true, true);
    var opt_dust = new Option("dust", "dust", false, false);
    select_elem.options[0] = opt_none;
    select_elem.options[1] = opt_dust;
 }
 else{
    select_elem.options.length = 0;
    var opt_none = new Option("none", "none", true, true);
    var opt_seg = new Option("seg", "seg", false, false);
    var opt_xnu = new Option("xnu", "xnu", false, false);
    var opt_segxnu = new Option("seg+xnu", "seg+xnu", false, false);
    select_elem.options[0] = opt_none;
    select_elem.options[1] = opt_seg;
    select_elem.options[2] = opt_xnu;
    select_elem.options[3] = opt_segxnu; 
 }
}

function setDatabaseOptions(program){
 var select_elem = document.getElementById('database_select');
 if (program == 'blastn' || program == 'tblastn' || program == 'tblastx' ){
    select_elem.disabled = false;
    select_elem.options.length = 0;
   
    var database_descriptions = [
    "Brassicaceae Repeats",
    "Fabaceae Repeats",
    "Gramineae Repeats",
    "Solanaceae Repeats",
    "----------",
    "Arabidopsis Repeats",
    "Brassica Repeats",
    "Glycine Repeats",
    "Hordeum Repeats",
    "Lotus Repeats",
    "Medicago Repeats",
    "Oryza Repeats",
    "Solanum Repeats",
    "Sorghum Repeats",
    "Triticum Repeats",
    "Zea Repeats",
    "----------",
    "Arabidopsis GSS Repeats",
    "Brassica GSS Repeats",
    "Glycine GSS Repeats",
    "Lotus GSS Repeats",
    "Lycopersicon GSS Repeats",
    "Medicago GSS Repeats",
    "Oryza GSS Repeats",
    "Sorghum GSS Repeats",
    "Triticum GSS Repeats",
    "Zea GSS Repeats",
    "----------",
    "Solanum lycopersicum de novo Repeats",
                                ];
    var db_ids = [
                    "1",
                    "2",
                    "3",
                    "4",
                    "",
                    "5",
                    "6",
                    "7",
                    "8",
                    "9",
                    "10",
                    "11",
                    "12",
                    "13",
                    "14",
                    "15",
                    "",
                    "16",
                    "17",
                    "18",
                    "19",
                    "20",
                    "21",
                    "22",
                    "23",
                    "24",
                    "25",
                    "",
                    "26"
                 ];
    var selected_flag = true;
    for (var i in database_descriptions) {
        if (i > 0) {
            selected_flag = false;
        }
        select_elem.options[i] = new Option(database_descriptions[i], db_ids[i], selected_flag, selected_flag);
    }
} else {
    select_elem.options.length = 0;
    select_elem.options[0] = new Option('=== None Available ===', "", true, false);
    select_elem.disabled = true;
 }
}

function changeProgramDesc(){
var selected_text;
var blast_select = document.getElementById('blast_program');
for (var i = 0; i < blast_select.options.length; i++) {
   if (blast_select.options[i].selected){
     selected_text =  blast_select.options[i].text;
   }
}
var blast_desc;
var seq_textarea;
var seq_file;
var search_type;
switch(selected_text)
{
case "blastn":
  blast_desc = "Search a nucleotide database using a nucleotide query";
  seq_textarea = "Enter a DNA FASTA sequence:";
  seq_file = "or upload a file of DNA FASTA sequence:";
  search_type = "Search selected nucleotide databases using blastn";
  if (detectBrowser.isGecko){
    document.getElementById('strand').style.display = "table-row";
    document.getElementById('word_size').style.display = "table-row";
  }
  else {
    document.getElementById('strand').style.display = "block";
    document.getElementById('word_size').style.display = "block";
  }
  document.getElementById('matrix').style.display = "none";
  break;    

case "blastp":
  blast_desc = "Search protein database using a protein query";
  seq_textarea = "Enter a protein FASTA sequence:";
  seq_file = "or upload a file of protein FASTA sequence:";
  search_type = "Search selected protein databases using blastp";
  document.getElementById('strand').style.display = "none";
  document.getElementById('word_size').style.display = "none";
  if (detectBrowser.isGecko){
    document.getElementById('matrix').style.display = "table-row";
  }
  else {
    document.getElementById('matrix').style.display = "block";
  }
  break;

case "blastx":
 blast_desc = "Search protein database using a translated nucleotide query";
 seq_textarea = "Enter a DNA FASTA sequence:";
 seq_file = "or upload a file of DNA FASTA sequence:";
 search_type = "Search selected protein databases using blastx";
 document.getElementById('word_size').style.display = "none";
 if (detectBrowser.isGecko){
    document.getElementById('matrix').style.display = "table-row";
    document.getElementById('strand').style.display = "table-row";
  }
  else {
    document.getElementById('matrix').style.display = "block";
    document.getElementById('strand').style.display = "block";
  }
  break;            

case "tblastn":
 blast_desc = "Search translated nucleotide database using a protein query";
 seq_textarea = "Enter a protein FASTA sequence:";
 seq_file = "or upload a file of protein FASTA sequence:";
 search_type = "Search selected nucleotide databases using tblastn";
 document.getElementById('strand').style.display = "none";
 document.getElementById('word_size').style.display = "none"; 
 if (detectBrowser.isGecko){
    document.getElementById('matrix').style.display = "table-row";
  }
  else {
    document.getElementById('matrix').style.display = "block";
  }
 break;

case "tblastx":
 blast_desc = "Search translated nucleotide database using a translated nucleotide query";
 seq_textarea = "Enter a DNA FASTA sequence:";
 seq_file = "or upload a file of DNA FASTA sequence:";
 search_type = "Search selected nucleotide databases using tblastx";
 document.getElementById('word_size').style.display = "none";
 if (detectBrowser.isGecko){
    document.getElementById('matrix').style.display = "table-row";
    document.getElementById('strand').style.display = "table-row";
  }
  else {
    document.getElementById('matrix').style.display = "block";
    document.getElementById('strand').style.display = "block";
  }
 break;
}
document.getElementById('program_desc').innerHTML = blast_desc;
document.getElementById('seq_textarea').innerHTML = seq_textarea;
document.getElementById('seq_file').innerHTML = seq_file;
document.getElementById('search_type').innerHTML = search_type;
setFilterOptions(selected_text);
setDatabaseOptions(selected_text);
return true;
}