Online translators have come a long way but they are far from perfect. They generally use a form of direct translation which can produce comical if not completely unintelligible results. You can test how unreliable they are by just translating a paragraph from one language to another and back again. Try pasting something from a newspaper into a translator and translating it back and forth. Every time you translate it, it gets further from the original text.
Online translators are particularly dangerous in business. Imagine that instead of hiring a native speaker to do your translation, you use an online translator. A native speaker visits your website and might be so put off by the bad translation that he/she decides just to try somewhere else. A restaurant menu seems like something that would be fairly easy to translate but if your customer has an allergy, he/she needs to know exactly what is being ordered.
How do you avoid doing a direct translation? First, you have to learn a significant portion of the source language and then constantly consult a good dictionary. Often the first translation given is not the correct one. You have to find the word or expression that fits the context.
Here is an article from the Huffington Post which has several examples of less-than-perfect translations.
Head of Studies