Looking for a good music theory website? I like musictheory.net. It’s easy to use in a regular web browser or smart device. If you have an iOS device (iPhone etc) you can buy an app that allows customization. But either way it’s very effective.
For beginning and elementary note reading, this is the page I use the most.
– clefs – grand staff
– range: less to make it easier, more to make it harder
– key signatures – just the one in the “middle” (no sharps or flats)
– note names – letters
– helpers – on if needed
– accidentals – off
– next question – I recommend “after audio”
so you can hear the pitch of the note you see
– challenge mode – off
Lots of other good pages too. Enjoy!