In a word, no.
Regardless of how the images are originally produced, re-sampling, (re-sizing), a raster based image will always have a detrimental effect...be that bigger or smaller.
Displaying images on a web page, regardless of what that it is, will almost certainly not be a vectored image, but rather a jpeg or png. Jpeg compression is good but it needs to be controlled when created...or more 'turned off' to get any reasonable image from it. PNG on the other hand is far more forgiving and nowadays with higher bandwidth internet the preferred format. The days of compressing images for faster web page loading are long gone.
Depending on the ultimate reason for these images will determine what happens to them.....are these jpg's being used as a link to the vectored version for download?
Your statement 'Drag the image to 100% size' is of little use without knowing where you are doing this but it does give a clue that the images you upload are only being converted to jpgs and not re-sized....unfortunately they then get a double wammy of not being displayed AT that size.....so not only have they been compressed to jpg but also not displayed at 100%.
If you need the vectored images to be available for download then I'd suggest creating your own 'uncompressed' PNG versions at the right size to be displayed [wherever] and get whoever to just make them a link to the vectored versions.
If you don't need a vectored image then do yourself a favour and just create the images in PS....one smaller version to fit in the web space allotted to it and the original for download....and in PNG format.
I may have completely misunderstood the question but there are many variables floating around in your situation which means there could be many varied solutions...too many to 'guess' which is right.
regards.
MrToM.
