Yes my pictures are so big that the quality is very low
That does not make any sense :-? The higher the resolution of your screen, the bigger your images will be and the better the quality when you resize them: squeezing 1600 pixels in to 800 'sharpens' an image instead of creating on like you did

This looks a little bit low-res - kinda pixellated and 'blocky'
That is because he compressed to 10K instead of 100K



) my uncompressed file was 390 kbs large... 









