Does Internet Speed check varies based on the browser

I wanted to see whether browser makes different while checking the speed of the internet.  I did  speed check test using speedtest.net  and four different browser and surprisingly all of them gave different results.

1: Safari  Version 4.0.3 (5531.9)
Download Speed: 17.16 Mb/s
Upload speed: 4.08 Mb/s

2. Firefox Version 3.6 (rv:1.9.2 Gecko 20100105)
Download Speed:15.84 Mb/s
Upload Speed:4.25 Mb/s

3. Chrome Version 4.0.246.0 (31780)
Download Speed:15.47 Mb/s
Upload Speed:2.17 Mb/s

4. Chrome Version 4.0.249.43:
Download speed: 17.65 Mb/s
Upload speed: 3.98 Mb/s

Looking at the results, it seems speeds varies based on the browser. You can see latest version of the Google Chrome has improves and you can see both the upload and download speed has increased.