Essentially, your "Internet Speed" is dependent on your connection with your ISP - that's what determines the bandwidth you have available. Its common for "speed" to vary throughout the day, and from day-to-day, a result of many things most of which are beyond your control. If you'd like to test your connection - and other components of your system - against a known standard, and perhaps get some tips for tuning and tweaking things to improve your system's 'net performance, try
PC Pitstop. Another useful online test suite is Fred Langa's
Browser Tune, and I think you'll find Jason Levine's
Jason's Toolbox a good resource for checking and tweaking browser security.
All of these are free, though email registration is required for full functionality. Don't worry; you can opt out of their email lists if you want to, and none will give your email to any 3rd party.