If the glass is tempered for strength, it cannot be cut without annealing it first. At that point, it may be cheaper to purchase a new top. Here is a link that might be useful: cutting tempered glass

Of course, guys cut window glass all the time to fit people's windows. They even cut mirrors & bevel. So you can get a glass cutting tool at home building store or take it to any hardware that cuts glass & they will charge you few bucks to do it. Several ways to smooth the edge but you want it to match the rest. If it fits down in a "groove"(table has an edge around it with piece all around that glass sits on so most of glass is down & hidden on edge even so use some wet/dry sandpaper on block of wood to smooth glass so no 1 gets cut as glass is very sharp. Just as you could use emery board to file off chip on grandma's 100 yr old china, you can smooth this edge but if glass cutter can do it let him, you might save yourself some cuts. Painful until you get it smooth so won't cut you at all. If glass sits on top it is little more tricky & corners need care so you don't damage top. Good Luck!

I used clear ones and for some reason when I removed the glass after quite awhile mind you, they had caused the wood where they rested to look lighter. I later was told that those rubber discs have some sort of acid in them that damages wood, especially if the wood is near a sunny window. Mine was not near a window however. I put the glass on the top of the table to protect it from my kids hoping that one day I could remove it, but now there are a number of strange looking spots.

i suppose then it depends on the thickness and weight of the glass. ours is on a double dresser, where i put on sunscreen and where icy drinks are often set, on the way to the deck off of our master bedroom. so the glass is rather large, no way it would slither off. yes, you can see the discs. but the glass guy made a good effort for them to be symmetrical, so thats something. here's something tho..... if a drink is left on for a while, there is actually condensation under the glass surface. it goes away again but its enough that i have to make sure a drink isnt abandoned there, or i'd end up with condensate dripping on my dresser where i cant even get to it to wipe it up! still better than sunscreen drips, tho.