Excessive salt can inhibit the growth of plants. Plants grown in containers have to make due with a limited amount of soil and anything in it will be reflected in the plant's growth and general vigor.
Don't wait until you start to see a whitish crust on the soil or sides of the pot. At least once a month, water your potted plants thoroughly, so that excess salts will be flushed out the drainage hole of the pot. Make sure you have a coaster under the pot, or move it to the sink or tub. make sure to remove any sitting water, which can cause the roots to rot.