A multilingual website is a website that is available in multiple languages. This could be an English website also offering its content in Spanish, or a Canadian website with articles in English and French for example.
Even though it is possible for a website to target just one single country of course, it's also possible for a website to aim at several countries at the same time. Apart from the pros and cons that will be discussed below, another noteworthy issue is at play, namely the topographic distribution of the target audience. This distribution creates an entirely different problem: in what country will the website be hosted? One of the aspects that determines how fast a website will load is the amount of 'hops' between the server on which the files are located, and the psychical location of the user's computer. Hops are seen here as jumps via internet hubs through which the packages (parts of files) must travel before finally showing up on your screen. A rule of thumb is that the closer your server is to your end-users, the faster the website will load for them. Even though there currently are solutions like Content Delivery Networks (CDN), it of course can never hurt to give the location of your server some thought.
There are in fact several ways to determine which language will be chosen for the end-user. For example we can use the language selected in the internet browser. Normally we can assume that someone who has his browser set to a certain language, he is also able to read text in that same language. Do keep in mind exceptions such as the usage of a computer in an internet café abroad.
An alternative is to use a so-called 'splash page'. These pages (often used historically to display Flash intros) presents visitors the opportunity to select their own preferred language for the website. Even though this might seem to be a user-friendly solution, it actually isn't, neither for human visitors and for search engines alike. There are a couple of reasons for this. Firstly the usage of this technique creates an extra click between a referring website or a search engine result, and your actual website. Secondly, many visitors will land on other pages than your front page. This would mean you would have to create another language selection option, for example by the usage of flags, to let those users selected their preferred language as well.
The largest (and probably only) pro of having a multilingual website is that you can address people in their own language. Instead of being confronted with a foreign language (in most cases English) that they might not fully, or might not at all, control, these visitors will now see your website in their own language. Visitors that might have exited your website before because they don't (fully) control the language it was offered in, might now possibly hang around longer, which in turn increases the changes of them contacting you or mentioning you on their social media platforms
Even though in some cases it might be possible to use Google Translate for the translations, in most cases native speakers will be required for the languages that you plan to offer on your website. You should also keep in mind that websites aren't static. You are very likely to add new content to your website, or will rewrite old pieces of content. Of course it's possible to leave the old translations up (or not translate new content at all), but if you didn't care to translate, why did you offer multiple languages in the first place? Another piece of consideration is that good translators often aren't cheap (and that the price depends on the source and target language as well).
Even apart from the fact that the translations have to stay up to date with the current revisions of the content, maintaining a multilingual website is more difficult than one offered in a single language. Articles will need to be linked across languages, and instead of creating a single article for a language, with a multilingual site, multiple articles will have to be created
Another point with multilingual websites is that they increase the difficulty of doing Search Engine Optimization (SEO). For example you will now have to consider multiple local versions of Google (for example google.nl and google.fr). Also, tags such as titles and descriptions should be correct across the multiple languages. It's also important to get links from different websites that are targeted on the same languages that you're targeting. This will improve Google's view of your website as an important source for speakers of that particular language
Even though the vast majority of languages you a writing from left-to-right, there are several languages that are written right-to-left. These languages are Arabic, Hebrew, N'Ko, Syric, Thaana, Tifinar and Urdu (source). When one or more of the languages that your website is targeting use right-to-left script, then you'll have to make sure that your website is capable of displaying the content correctly for that script.
Not just the styling but also the Content Management System should be capable of dealing with multiple languages. For example the system should be able to create articles in different languages and offer ways to link these articles together. From Joomla version 1.6 it's possible to do this type of multilingual management without the need for third party components.
The characters used in the content should be present in the font used for that page. The font that is used for this particular website is well-equipped to handle the English language. However, when a website is using languages that use different characters (for example Chinese, Russian or Thai) than you'd better make sure those characters are present in the font that is used. It is assumed that there are 13 web-safe fonts which you can use to display the most commonly used languages. Another point of consideration is that the amount of space used per word is can differ between languages.
When you offer your website in multiple languages, soon or later people will start contacting you in one of these languages as well. When you've used external translators to handle the translation of the website, this might lead to problems. It's therefore advised to explicitly state on your website which languages customers are allowed to use to contact you. In the rare cases that people will contact you in a foreign language anyway, you could try to use Google Translate to make sense of it. A tip is to translate your message back-and-forth in Google Translate to make sure it doesn't contain anything all too weird.
The cost of a multilingual website are strongly depend on the scale of that particular website, whether or not your control these languages yourself and the thoroughness of which the website needs to be translated. In general you can assume a fairly large surplus to the price when a website needs to be built multilingual.
The time required to build a multilingual website is vastly larger than a single language website. As explained above there are several issues related to making a website multilingual, which virtually all required additional time to be invested.
One should weigh the benefits of being able to offer languages in the visitor's native language against the cost in terms of time and money that have to be invested (and will need to continue to be invested).
Image credits: Flags