Just eating salads (and no other kind of food) will not be the answer to lose weight and be healthy.
Salads are ESSENTIAL to your health, however you should mix and match them with other nutrient/vitamin rich foods such as: fruits, vegetables, protein etc.
You should always eat leafy greens, tomatoes, carrots, grains in your salads. Avoid using ready made sauces (bottled ones), as they are rich in salt and other bad ingredients. Prefer natural "sauces" such as lemon, vinegar or even olive oil.
Make sure you also cook your own salad. Boxed salads are also no good as they probably were not prepared with the fresher ingredients. It can also be a great source of bacteria if its ingredients were not washed properly.
Overall avoid fast foods, carbonated drinks and snacks, that way you will definitely lose weight and remain healthy!