Getting Bootstrap's modal content from another page

Update

The way you're trying to get modal's content from another page is incorrect.

According to Bootstrap's documentation:

If a remote URL is provided, content will be loaded one time via jQuery's load method and injected into the .modal-content div. If you're using the data-api, you may alternatively use the href attribute to specify the remote source. An example of this is shown below:

<a data-toggle="modal" href="remote.html" data-target="#modal">Click me</a>

So, firstly, you should change your menu.html file to be similar to the code above:

<li><a href="Lab6.html" data-target="#theModal" data-toggle="modal">Lab 6</a></li>

And then, part of your Lab6.html page must reside inside your menu.html page. E.g:

<div class="modal fade text-center" id="theModal">
  <div class="modal-dialog">
    <div class="modal-content">
    </div>
  </div>
</div>

Finally, your LAB6.html would have only the code that was inside .modal-content. E.g:

<div class="modal-header">
  <button type="button" class="close" data-dismiss="modal">X</button>
  <h1>Lab 6</h1>
</div>
<div class="modal-body">
  <div class="panel panel-default">
    <div class="panel-heading text-center">
      Employee Information
    </div>
    <div class="panel-body">
      <div class="row">
        <div class="text-right col-xs-2">Title:</div>
        <div class="text-left col-xs-3" id="title"></div>
        <div class="text-right col-xs-2">First:</div>
        <div class="text-left col-xs-3" id="firstname"></div>
      </div>
      <div class="row">
        <div class="text-right col-xs-2">Phone#</div>
        <div class="text-left col-xs-3" id="phone"></div>
        <div class="text-right col-xs-2">Email</div>
        <div class="text-left col-xs-3" id="email"></div>
      </div>
      <div class="row">
        <div class="text-right col-xs-2">Dept:</div>
        <div class="text-left col-xs-3" id="departmentname"></div>
        <div class="text-left col-xs-2">Surname:</div>
        <div class="text-left col-xs-4">
          <input type="text" placeholder="enter last name" id="TextBoxLastName" class="form-control" />
        </div>
      </div>
    </div>
  </div>
  <div class="modal-footer">
    <div class="panel-footer">
      <input type="button" value="Find Employee" id="empbutton" />
      <div class="col-xs-10" id="lblstatus"></div>
    </div>
  </div>
</div>

Take a look at the plnkr I created for you.

Note that if you are using Bootstrap 4, the accepted answer does not work, because according to Bootstrap's docs about the remote option:

This option is deprecated since v3.3.0 and has been removed in v4. We recommend instead using client-side templating or a data binding framework, or calling jQuery.load yourself.

If a remote URL is provided, content will be loaded one time via jQuery's load method and injected into the .modal-content div. If you're using the data-api, you may alternatively use the href attribute to specify the remote source. An example of this is shown below:

<a data-toggle="modal" href="remote.html" data-target="#modal">Click me</a>

To make it work, first remove the data-target and data-toggle attributes from the link. You can leave the href attribute there.

<li><a href="Lab6.html" class='li-modal'>Lab 6</a></li>

Using jQuery we can add a click listener to the <a> element, but we do not want to directly go to the page indicated by the href attribute so we use preventDefault(). By simply using jQuery's load method we can load the content of the lab6.html page into modal-content.

$('.li-modal').on('click', function(e){
      e.preventDefault();
      $('#theModal').modal('show').find('.modal-content').load($(this).attr('href'));
    });

Full example here.