Random "Pronouncable" Password Generator

this script lists the basic elements of a word and chooses a random word structure to make the word pronouncable... or... at least 50% of them ;). I'm sure there is a way to do this to cut down on the code... but here goes anyway...

<script>

/****************************************
* *
* Random "Pronouncable" Password Script *
* *
****************************************/

var letters = "bcdfghjklmnprstvwxyz";
var vowels = "aeiou";

groups = new Array();
groups[0]="th";
groups[1]="ch";
groups[2]="sh";
// groups[3]="qu";

function generate(number) {

// randomize letters

var vowel1 = vowels.charAt(Math.floor(Math.random()*vowels.length));
var group1 = groups[Math.floor(Math.random()*groups.length)];
var letter1 = letters.charAt(Math.floor(Math.random()*letters.length));
var vowel2 = vowels.charAt(Math.floor(Math.random()*vowels.length));
var group2 = groups[Math.floor(Math.random()*groups.length)];
var letter2 = letters.charAt(Math.floor(Math.random()*letters.length));
var vowel3 = vowels.charAt(Math.floor(Math.random()*vowels.length));
var group3 = groups[Math.floor(Math.random()*groups.length)];
var letter3 = letters.charAt(Math.floor(Math.random()*letters.length));
var vowel4 = vowels.charAt(Math.floor(Math.random()*vowels.length));
var group4 = groups[Math.floor(Math.random()*groups.length)];
var letter4 = letters.charAt(Math.floor(Math.random()*letters.length));

// specify the structure of the words (in order for them to be pronouncable)
// feel free to add your own...

structure = new Array();
structure[0]=letter1+vowel1+letter2+letter3+vowel2+letter4+vowel3+group1;
structure[1]=group1+vowel1+letter1+letter2+vowel2+letter3;
structure[2]=group1+vowel1+letter1+letter2+vowel2+group2;
structure[3]=group1+vowel1+letter1+vowel2+"s";
structure[4]=vowel1+group1+vowel2+letter1+vowel3;
structure[5]=group1+vowel1+letter1+vowel2+group2;
structure[6]=vowel1+group1+vowel2+letter1;

var password=structure[Math.floor(Math.random()*structure.length)];

if (number==1) {
document.passform.passbox.value=password+Math.floor(Math.random()*100)
}
else {
document.passform.passbox.value=password;
}
}
window.onload=generate
</script>

<div align="center">

<table>
<tr>
<td colspan="2" align="center" style="font-family: verdana; font-size: 12pt; font-weight: bold;">
Random "Pronouncable" Password Generator
</td>
</tr>
<tr>
<td>
<form name="passform">
<input type="text" name="passbox" style="font-family: verdana;" onfocus="this.select()" /><br>
</td>
<td>
<input type="button" value="Generate! (Words Only)" onclick="generate(0)" style="font-family: verdana" />
<td>
</tr>
<tr>
<td>
&nbsp;
</td>
<td>
<input type="button" value="Generate! (With Number)" onclick="generate(1)" style="font-family: verdana" />
</form>
</td>
</tr>
</table>
</div>