mjhjmtu

In my raspberry pi when I go to http://localhost/ I see a Apache2 debian default page,

So I went to

/var/www/html/index.html

and changed the source code to see if there were any changes in the page, and there aren't.

So, there's some other server running and sharing the same folder maybe?

sudo netstat | grep apache 

shows nothing, neither does httpd

If wget -O - http://localhost fails, then it must be coming from the browser cache.

You are making several simple mistakes.

Firstly, the port service name for the HTTP/HTTPS services is named http or https and not apache.

For checking the service name:

$ grep http /etc/services 
http 80/tcp www # WorldWideWeb HTTP
https 443/tcp # http protocol over TLS/SSL
http-alt 8080/tcp webcache # WWW caching service
http-alt 8080/udp

Secondly, to see listening services you have to give the -a option to netstat.

So, you should be running:

netstat -a | grep http

or:

$ netstat -a | grep LISTEN | grep http
tcp 0 0 0.0.0.0:http 0.0.0.0:* LISTEN 
tcp 0 0 0.0.0.0:https 0.0.0.0:* LISTEN 

You could also check Apache is running checking the process:

$ ps ax | grep apache
 2362 ? Ss 0:00 /usr/sbin/apache2 -k start
 2366 ? S 0:00 /usr/sbin/apache2 -k start
 2367 ? S 0:00 /usr/sbin/apache2 -k start
 2368 ? S 0:00 /usr/sbin/apache2 -k start
 2369 ? S 0:00 /usr/sbin/apache2 -k start
 2370 ? S 0:00 /usr/sbin/apache2 -k start
23476 pts/0 S+ 0:00 grep apache

So then you know Apache is running.

As for the page change: If using Debian or raspbian, the default is indeed /var/www/html. The most probable thing is being the former version cached in the browser. At most, the default configuration could have been changed, but I guess you would remember doing it.

As for caching pages, your browser might not be entirely at fault. If you want to signal some page is not to be cached, you have to return headers signalling data to client software (browser, proxies).

Namely these headers:

Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Expires: 0

You alternatively signal that you do not want particular pages cached in HTML:

<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
<meta http-equiv="Pragma" content="no-cache" />
<meta http-equiv="Expires" content="0" />

See for more details: How to control web page caching, across all browsers?

P.S. Obviously signalling that you do not want pages cached is more useful for HTML pages with dynamic content. However, due the nature of the question, this situation was explored to try to explain your browser might be behaving as it is expected of it.

corollary: As a former Galician mentor of mine used to say, the important part of having tools, is understanding how they behave before putting them at fault.