There are many free and paid Spanish translation services available online, and some of the free ones are very good for short fragments of text or to get a general idea about the meaning of a website. Many webmasters use them to translate websites on demand and reach a wider audience. However, you should know a free Spanish translator is never as accurate as a paid human translation.
Accuracy of machine translation
Many paid translation services use a mixture of human and machine translation to deliver the most accurate translation. Free Spanish translators, however, only use machine translation which is not accurate and thus cannot deal with subtler aspects of foreign translation.
Not all languages can be automatically translated to Spanish
The accuracy of a machine translation will depend on the source and target language, since some languages are more similar in both structure and usage than others. For example, if you attempt to translate Korean to Spanish, the result is probably going to be plagued with grammar errors, misaligned verb tenses and genders etc. However, the same exercise with an Italian translator will probably yield much better results. Idioms
A typical problem for a free Spanish translator are idioms. Idioms are sentences with their own meaning that is given by use and not by the words in the sentence. A literal translation gives funny meanings. For example, the idiom "In for a penny, in for a pound" in Spanish becomes "De perdidos al rio", which literally means "From lost to the river". This has lead to many fun misunderstandings for both tourists and people trying to translate online articles to republish them.
Suitable uses of a free Spanish translator
There are many online Spanish translators such as Babylon free or Google Spanish translation that can be used to get the meaning of a paragraph or a website, but shouldn't be used without human revision to publish content in an alternative language.
Free website translations
If you have a website with useful content and you want to make it available to Spanish readers, it's usually acceptable to implement an automatic translation option. The person reading your website is after knowledge, and won't care so much if the verbs aren't properly used or there are a few mistakes with the gender of words. Getting help online
Free online translators can be used easily to understand answers to questions originally posted in Spanish. Generally speaking, the translation from Spanish to English is much more accurate than from English to Spanish, specially since Spanish has a more complex grammar as regards gender and number declinations. Generally speaking, translating single words for vocabulary is pretty accurate, while long complex paragraphs may become confusing.