There is a tendency among designers of websites to use small images of flags to denote languages. We think this is a bad idea.
First, let us see who might be tempted to use flags on websites. We think this is an easy trap to fall into if it so happens that you live in a country with a name that corresponds to the official, or at least the dominant language spoken there. There are many such examples that I am familiar with: Deutschland -- Deutsch, France -- Français, Sverige -- Svenska, Việt Nam -- Tiếng Việt.
However, this exact correspondence between the name of the country and a language is actually quite rare. In fact several of the examples above are not as pure as they might seem to an outside observer, or even to a person that happens to have the dominant language as native language. In Sweden, several people speak some Sami language; in France, people speak Basque, Breton, Alsatian, Occitan; etc.
Perhaps you could now object that Sápmi has a flag that can be used to designate the Sami language, but then you do not take into account that there is such great variation within the Sami languages that the speaker of one may not understand the speaker of another.
Interestingly, there is a place where there is a fairly good correspondence between the name of the country and the language spoken, and that is England -- English. It is a curious fact that most designers of websites have chosen to use the Union Jack (a symbol of the United Kingdom, rather than the flag of England to designate English. There are exceptions though: in Vietnam, many automatic teller machines use the English flag to designate the English language.
The main problem with flags is that they are political symbols rather than linguistic symbols. The use of flags as linguistic symbols creates two problems:
The tendency to use flags on websites is a bit of a puzzle to me, because there are perfectly simple and unambiguous symbols for languages, namely the name of the language in the language itself. Perhaps designers of websites are tempted to sacrifice clarity and precision to make their sites more colorful. I strongly suggest they resist this temptation.