Insert external page with AJAX - how to limit CSS and Javascript for only one DIV-container

Question

I'm trying to insert an external website into a parent website. I'm using the following method to prepare the content:

jQuery.ajax({
    type: "POST",
    url: url,
    xhrFields: {
      withCredentials: true
    },
    crossDomain: true
}).done(function (result) {
    ...
    embedDiv = document.getElementById("embedDiv");
    embedDiv.innerHTML = result;
)}

Now, while all the CSS and Javascript Code is working perfectly, it also takes effect on all the elements of the parent page. Is there a way to restrict all the loaded sources to only work within the div container "embedDiv"?

Thanks for any clues!