user54613: So I just got my two ESP8266/ESP-12E WiFi development boards in the mail as I am trying to set up a few home automation devices in my house. I've gotten much further than I thought I would today, considering this is my first foray into working with circuits that involve microprocessors/WiFi, but I've run into a problem that I can't find a solution to myself.  Forgive me if there is another question similar to this, but I could not find it and this seems like the best place to ask.
I am using a tutorial/template program that Rui Santos from Random Nerd Tutorials was kind enough to create ( https://randomnerdtutorials.com/esp8266-web-server/ ), and although we have (as far as I can tell) identical boards, operating systems and Arduino code, I keep getting an HTML page that is text only, with none of the CSS or HTML elements showing.  It should look like this:

However, I am getting a page that looks like this:

His serial monitor is giving this response:

My serial monitor is giving me this response:

I've tried putting client.println("Content-type:text/html"); in a few places to see if it would help display the page, but to no avail.  Any help with getting this little program/website running would be greatly appreciated. 
Thanks for your time! 

user31038: Don't use the low-level tools to handle http, use the built-in http tools. They  make creating http responses trivial. No more concatenating headers or worrying about client status; it provides a nice clean function ex:server.send(404, "text/plain", message); and nice subscription method: server.on().
Checkout its usage on one of the Arduino ESP8266's built-in examples:
https://github.com/esp8266/ESPWebServer/blob/master/examples/HelloServer/HelloServer.ino

54613: <p>So I just got my two ESP8266/ESP-12E WiFi development boards in the mail as I am trying to set up a few home automation devices in my house. I've gotten much further than I thought I would today, considering this is my first foray into working with circuits that involve microprocessors/WiFi, but I've run into a problem that I can't find a solution to myself.  Forgive me if there is another question similar to this, but I could not find it and this seems like the best place to ask.</p>

<p>I am using a tutorial/template program that Rui Santos from Random Nerd Tutorials was kind enough to create ( <a href="https://randomnerdtutorials.com/esp8266-web-server/" rel="nofollow noreferrer">https://randomnerdtutorials.com/esp8266-web-server/</a> ), and although we have (as far as I can tell) identical boards, operating systems and Arduino code, I keep getting an HTML page that is text only, with none of the CSS or HTML elements showing.  It should look like this:</p>

<p><a href="https://i.stack.imgur.com/5d5OA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5d5OA.png" alt="expected outcome"></a></p>

<p>However, I am getting a page that looks like this:</p>

<p><a href="https://i.stack.imgur.com/531q1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/531q1.png" alt="outcome"></a></p>

<p>His serial monitor is giving this response:</p>

<p><a href="https://i.stack.imgur.com/jgXDf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jgXDf.png" alt="his serial monitor"></a></p>

<p>My serial monitor is giving me this response:</p>

<p><a href="https://i.stack.imgur.com/hkodX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hkodX.png" alt="my serial monitor"></a></p>

<p>I've tried putting <code>client.println("Content-type:text/html");</code> in a few places to see if it would help display the page, but to no avail.  Any help with getting this little program/website running would be greatly appreciated. </p>

<p>Thanks for your time! </p>
 31038: <p>Don't use the low-level tools to handle http, use the built-in http tools. They  make creating http responses trivial. No more concatenating headers or worrying about client status; it provides a nice clean function ex:<code>server.send(404, "text/plain", message);</code> and nice subscription method: <code>server.on()</code>.</p>

<p>Checkout its usage on one of the Arduino ESP8266's built-in examples:
<a href="https://github.com/esp8266/ESPWebServer/blob/master/examples/HelloServer/HelloServer.ino" rel="nofollow noreferrer">https://github.com/esp8266/ESPWebServer/blob/master/examples/HelloServer/HelloServer.ino</a></p>
