ESP8266 library: 2 requests received instead of 1
Browsers automaticaly request /favicon.ico for sites. Add this to &lt;head&gt; section of your HTML to eliminate the 'favicon' request: 

&lt;link rel="icon" href="data:;base64,iVBORw0KGgo="&gt;

client.println("HTTP/1.1 200 OK\r\n" "Content-Type: text/html"); 
client.println("Connection: close"); 
client.println(); 
client.println("&lt;!DOCTYPE HTML&gt;"); 
client.println("&lt;html&gt;&lt;head&gt;"); 
client.println("&lt;link rel='icon' href='data:;base64,iVBORw0KGgo='&gt;"); 
client.println("&lt;/head&gt;&lt;body&gt;"); 
client.println("Hello World!"); 
client.println("&lt;/body&gt;&lt;/html&gt;");


based on this SO answer, instead of pointing to a server, the icon is encoded in the href parameter as base64 string