Modern browsers give the user a chance to configure which languages they understand. The order in which languages are listed gives the users preference if an internet page is available in different languages.
In the menu "Edit" choose "Preferences". In the preferences windows click on "General" in the left pictogram list. In the right part of the window click on "Languages..."
To add a language, press Select a language to add..., choose the language, and click the Add button. Remove a language by selecting it in the list of active languages and clicking the Remove button.
You can reorder languages to determine the preferred one in case a page is provided in two or more of your selected languages. Do this using the Move Up and Move Down buttons. more...
By default konqueror automatically uses the settings configured when you installed your desktop. You can manually override this behavior by adding the following settings to either $KDEHOME/share/config/kioslaverc or $KDEHOME/share/config/kio_httprc:
If you add the settings to the first "kioslaverc", then the options are available to all KDE ioslaves that support changing these settings. On the other hand, if you want the settings to be applicable to a specific io-slave, e.g. kio_httprc, then you want to add them to the protocol specific config files. more...
In recent versions of Opera (8.x) choosse "Preferences" from the "Tools" menu. On the "General" tab you can select the language in the bottom part of the tab. Klick on "Details..." to build and sort your preference list if you understand more than one language.
In IE 3 or 4, select "Internet Options" from the "View" menu. In IE 5 or 6 the menu option "Internet Options" is in the menu "Tools". On the "General" page, select "Languages" use the button "Add..." to add languages to the list as necessary. Select one language in the list and use the buttons "Move up" and "Move down" to arrange the languages in order of preference. Click OK to save the changes
For a more complete list of browsers and their language settings look at debians page on different languages