If I jog every day...will I gain weight..?

Try walking briskly instead. running or jogging will cause your legs to gain muscle while walking fast will burn fat. A good friend of mine lost 50lbs when he started walking home from school (about 1.5 miles) everyday.

Well it depends on how much you jog and how fast.

Little sally eats 4000 calories a day and walks for an hour while holding the handle bars the whole time. Sally then wonders why she lost no weight after a week from just moving her legs at a lazy speed. While working out Sally may have only burned 120 instead of the 420 the machine said.

Say your diet is 3000 calories which is about normal. You should lose about 1800 just from being alive and you would need to burn about 800 to lose weight and like 600 to maintain weight. You don't lose weight just from doing any workout though because it depends on how much you eat and how much you actually burned. Not what a machine assumes you did.

I thought jogging was to firm muscles and you lose weight too, good combination.

you may gain a few pounds initially because of muscle gain, but then lose fat, so it'll even out..

but if you don't want muscle just don't do hills

Yep, jogging will make your skin and body tight which then will make you look fit. Drink plenty of water aswell.

your thighs will become more muscular if you jog, yes.