You can achieve that by changing the selected value when the user focuses on the select onfocus="this.selectedIndex = -1".

<select name='m-menu' onfocus="this.selectedIndex = 0" onchange='location = this.options[this.selectedIndex].value;'>
  <option value="" style="display: none">Select an Item</option>
  <option selected value='/users/lol'>My Account</option>
  <option value='/?signout'>Sign Out</option>
  <option value='/photos'>Photos</option>
  <option value='/post'>Share/Post</option>
  <option value='/feed'>Feed</option>
  <option value='/chat'>Create Chat</option>
</select>

I would also suggest you add your event listeners from a separate javascript file instead of using the on* attributes. You can do that using addEventListener