Could anyone help me with this query please?

I've written a simple WebGL app that draws some lines.

It works fine.

I'm using Firefox.

When I point the browser at the file directly on the HDD it looks great, but when I point the browser at the same file via my localhost server (I'm running Apache on Windows) the lines don't look so nice, they seem aliased. Moreover, a diagonal line seems more "steppy", less smooth.

Why the difference,