Caveats: Last I checked, Safari did not run the score browser correctly. Firefox and Chrome should be okay. I will try to find time to cater to Safari in future. As for MicroSoft IE, I doubt I will ever bother to test it even. Also, the browser was developed for desktop/laptop use, and may still have glitches when used on a touchscreen device, esp. one where your finger is large relative to the screen.
There's not much to it—you move the ‘magnifier’ around the pages of the score to get a clear view. If parts of the score are still closed to you, the magnifier simply won't show clear images over those parts. You ‘turn pages’ within a score by dragging/swiping left or right. Dragging/swiping up or down flips through the available scores.
The purpose of the score browser application is to grant controlled online access to parts of the scores. The extent of access is related to your purchase and donation history. A newcomer will be able to test the app on the free scores (R.125, R.159, and R.183); access to other scores remains quite limited without some investment. My intention is to encourage some expenditure (I need to eat like anyone else), but the app is also useful in helping you choose works based on the visible excerpts.
Note that donations are actually credits toward purchase, so it is worth donating first in order to open up more territory in the browser before deciding on works. I should also mention that the quality of the scores you purchase are 300 dpi (dots per inch), which may be higher than what is shown in the score browser. To see the actual quality of purchased scores, you can take the free scores as exemplars.The resolution shown in the magnifier depends on how large your browser screen/window is. If the default is too small you can increase it by adjusting the Mag. text field; values between 0.2 and 0.9 are valid, with 0.45 being the default.
The view in the magnifier fades unless you are moving it. This is not so much a feature as a deliberate limitation of the browser. You can click/tap to freeze the magnifier view and stop it from fading; on your next movement it will again start fading when not being moved. Obviously the scores would be more readable if I just provided the full page images—but then there would be no point in trying to sell them, as nobody would pay for anything, and I would literally suffer for it. My music is more ‘open’ than typical, so if the score browser sometimes seems frustrating, you need to remember it is there to help guide your purchases, not for reading complete scores through.
The score browser app should work on most browsers, including mobile. No doubt there are bugs, and if it seems to be misbehaving the best remedy is to reload the browser window. If you experience persistent problems, feel free to send email.
I can't resist taking this opportunity to remind you that, if you buy a song, you are entitled to automatic updates when the score is recopied. At this time a lot of the scores are a bit rough, but I am recopying all the time and I expect that by mid-2018 most of the scores should be pristine. In fact, recopying has been slow. I'll be fair-copying on demand, rough drafts being adequate for my own use. Since the prices are set proportional to the neatness of the score (among other factors), if you buy a song early when the score is still rough, you save money since you get the latest scores for free (emailed unless you declined email updates; downloadable for free otherwise).