Most probably you are using one of the Sitefinity versions before 3.6. From 3.6 we are using dynamic links. However, by default we resolve the relative path and the culture is skipped. This means that the url is opened depending on your current culture. If your current culture is "en" the format of a page your will be "domain.com/en/page.aspx
". When your current culture is different ( say "bg") the url format will be "domain.com/bg/page.aspx
In your case you could upgrade your project or try enabling module localization. When module localization is enabled the path prefix should depend on the language version of your content item.
the Telerik team