web jpg image quality compression thoughts, suggestions, experiences in use with phot

Hello,
I have put up a lot of web galleries online with photoshop's web gallery tools and now also using some lighroom.
I have experimented a bit with the different quality settings for the images and have a hard time seeing much difference in almost all of the images weather it be compressing to a quality of 50 (lighroom) / 5 (photoshop) or kept at a quality of 100 / 10. The difference of web viewing on a normal sized desktop seems pretty much unnoticeable.
When using very low qualities such as 20 / 2 I can see obvious fragmenting and pixelation and it looks terrible, but not at 50 / 5. It seems that there should be a lot more of a perceptable difference of quality between 50 / 5 and 100 / 10. If this is the case, I'd rather use a quality of 50; but I feel like I shouldn't use such a low quality.
Is there something I am missing.
What sort of jpg quality do you often use with your galleries. Would you recommend going against a 50 / 5 quality if you can't tell a difference?