[naak2803]

<form action="demo_form.asp">
RegNr: <input type="text" name="regnummer">
<input type="submit" value="Submit" onclick="searchURL();">
</form>

<script>
function searchURL(){
var vTxtValue = document.getElementsByClassName("regnummer")[0].value;
window.location = "www.hemsida.se/regnummer=" + vTxtValue;
}
</script>