This is a very simple progress bar I found on html-online.com which is using only HTML, CSS and JavaScript. It runs well on every major browser if JavaScript is not disabled.
You can see how it works on the demo below or see my own custom implementation for the online Rubik's Cube solver program.
All sliders I could find out there were using flash or images and they all had unnecessary functions. The progress bar you can find here doesn't load any images just some CSS code to style the bars. All you have to use is a JavaScript function, some styling and to place the HTML code where you want the slider to appear on the page. Of course you have to call the function whenever you want to refresh the percentage.
You can download the code here: The Most Simple Progress Bar
Please let me know in the comment section below if you have any difficulties using this plugin.