Most likely the isp try this
Test your broadband link
you latency times may be killing your speed ( Esp Time Warner Cable & Comcast)
Strange but running the above test kills my internet connection 3 times out of 4 tries.
The one time it didn't it returned an error after the 90 second test indicating it couldn't see my machine.
The three times it killed my connection I had to do a hard reset of my combination modem/router.
I fail to see why this test is any better that the Speedtest.net test performed by the OP.
Speedtest measures your latency as well.
Latency is dependent on the server doing the testing.
In my case Speedtest.net chooses a server in Boise, Idaho as the default test server.
Latency for the server in Boise is 150ms.
Changing the test server to one in Salt Lake City, Utah I see a latency of 82ms and testing at a server in
San Francisco, Ca. gives 53ms.
Not that physical difference matters but the air distance from me in Elko, Nevada to the various servers
is
415 mi to San Francisco
186 mi to Boise
196 mi to Salt Lake City
As can be seen latency is dependent on the server used for the test.
In all cases the raw speed measured almost exactly the same.
Finally a test using a server in Amsterdam, Holland
As can be seen above latency is all over the place.
Ping=Latency
BTW, the test site suggested by Ghost Writer will only measure 4 times in one 24 hr period,
regardless of whether test was successful or not.
I would really like to know why it killed my internet connection,
I've never seem a web site do this before.