Mary, my post crashed. It was quite technical and lengthy, so probably just as well. Just to let people know that salt is actually used quite commonly in sourdough starters, usually around 2% of the total starter weight. In German, it is called the "Monheimer Salzauer Verfahren," after the German baking scientist Herr Monheimer, who also gave the world the 1, 2 and 3 stage starter processes (basically, 3 stages where at each stage varying starter thickness, temperature and time optimizes yeasts, lactic acid bacterias, and acetic acid bacterias at each stage).
Yeast can tolerate a fairly high amount of salt - IIRC, up to 8%. So at 2%, they're fine, though they ferment at a much slower rate. Which is why this process is useful. Say, you want to bake next morning at 8 am. Say you have only so much oven space, but want to bake more than one type of sourdough. Normally, without salt, you might take your starter and do a pre-dough starter at room temperature and have a fairly tight window of 12 hours, before the starter is past its peak development and starts to recede.
The salt-sourdough process gives a huge window, anywhere from 16-24, before it starts to weaken and slack. So you can very easily plan for multiple loaves the next day.
The other thing about salt in starter is that whereas yeast has a fairly high salt tolerance, the lactic and acetic acid bacterias have a much lower tolerance. So, by adding a small amount of salt, you are really slowing the bacterias, and consequently limiting the acids produced - which really helps the yeast out.
A lot more, including the way traditional French bakers use salt in making and managing the initial stages of new starter, but that's probably enough here. If people would like more, including specific processes and recipe examples, please let me know.