Javascript select box clear when I press back button in browser


I have 2 select boxes on my web page - 1 for country and one for prov/state as below:
and I have attached my js file.

It works fine except when I go to the next page and then press the back button, the prov/state select box
is empty - the country select retains the value selected.

How do I fix this?

<select id=“txtCountry” type=“text” name=“country” onchange=“GetStateProv();”>
<option value=“”></option>
<option value=“Canada”>Canada</option>
<option value=“United States”>United States</option>
<option value=“United Kingdom”>United Kingdom</option>

  <span style=“margin-top:3px;”>State/Prov:</span> 
<select id=“txtStateProv” type=“text” name=“state-prov”>

Form names should never have hyphens in them as it causes cross browser issues and issues like the one you described above, simply change state-prov to state_prov or stateprov and it should work fine after that.