http://www.interfacesketch.com

Claim 1: white-ish lines on light grey paper.

Claim 2: As above, but more closely matching white and grey.

Claim 3: Either of the above but with a slightly colored paper instead of gray.

"On Whitelines there is no visual interference between the lines and the pen colour."

So, the lines on the paper are different depending on the color of the ink I'm writing with?

I always end up going to Wikipedia to understand what the company is selling.

    .line {
        background: rgb(233, 233, 233);
        height: 3.125em;
        border: 0.25em solid white;
        width: 100%;    
    }

Remember that dpi only controls print quality not print measurements. One cm printed at 300dpi will have the same length as one cm at 72dpi.

Still, this is very nice, it's easy to see the potential for other features.

very nice idea, very nice execution. Few things that imho need to be fixed (probably fast fixes): 1) Ensure that the print settings are correct. i.e. the pattern get splitted on two pages, for no reason. 2) resizing the browser window stretches/squeezes the picture. You shoud probably listen to the resize events and re-trigger the generation, change the patterns to some css, or simply set the generated image as cover. 3) translate the code in english. In softwares, having standards is a good thing.