If you've seen it done in another plugin (the version of Biohazzard that I was able to get did not have any HTML in the lang file). If you have a version that does it, you should post the lang file so we can see how they do it (in fact, if you knew of a source that already did it, you should have used that as your template/example).
If it was going to work, you would probably need to put it all on one line with NO whitespace (i.e. all a single line) and make sure to escape all reserved characters (e.g. %).