Below are a few links to popular services for testing sites.
Checking site loading speed:
https://developers.google.com/speed/pagespeed/
https://tools.pingdom.com/
https://www.webpagetest.org/
https://gtmetrix.com/
Test site in different browsers:
https://browsershots.org/
Site test for the number of connections:
https://loadimpact.com/
Spellchecker:
https://tech.yandex.ru/speller/
Check site availability:
https://www.host-tracker.com/
https://ping-admin.ru/free_test/
Other services:
https://www.yougetsignal.com
https://builtwith.com
https://www.onlinewebcheck.com
Tip: in order for Google to search only a specific site, you must add the name of the site at the beginning of the search line, for example: site:ixnfo.com REQUEST