<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script>
function validar()
{
document.getElementById("ver").disabled="disabled";
for(var i=0;i<document.getElementsByTagName("select").length;i++)
{
if(document.getElementsByTagName("select")[i].value==0)
return false;
}
document.getElementById("ver").disabled=false;
}
</script>
</head>
<body>
<select onchange="validar()">
<option value="0">Selecciona</option>
<option value="1">opción 1</option>
<option value="2">opción 2</option>
<option value="3">opción 3</option>
</select>
<select onchange="validar()">
<option value="0">Selecciona</option>
<option value="1">opción 1</option>
<option value="2">opción 2</option>
<option value="3">opción 3</option>
</select>
<select onchange="validar()">
<option value="0">Selecciona</option>
<option value="1">opción 1</option>
<option value="2">opción 2</option>
<option value="3">opción 3</option>
</select>
<button id="ver" disabled>Ver</button>
</body>
</html>
Comentarios sobre la versión: Versión 1.0 (1)