First I'll say the advice from TheRaptor is generally correct: the validator expects you to have a meta tag stating both the MIME type of the document (text/html) and the character encoding.
But it does get more complicated than that. The example given to you by TheRaptor is the same I use, but... and this is a big butt... my documents are also saved as UTF-8. This is important.
Originally, the validator told you it was going to assume your page was windows-1252. It probably saw something in your document that's special to that Windows version of Latin-1 (ISO 8859-1). Mostly, those two are the same, but there is a range of characters where the Windows version is different (0x80 - 0x9F) and so your x94 is one of those.
Usually those characters are the " and ' type.
Also in play is how your hosting server is sending the page out. While browsers are generally ok being given a page that's really Windows-1252 but told by the meta tag that it's Latin-1, if the server says for example that the page is UTF-8, then there's a problem. Whatever the server says is supposed to override what the meta tag in the page says. Which means the browser is told to read the page however the server says, and this won't work very well if the page simply wasn't created and saved that way.
Second: somewhere in the program you're using, there's an option in the menu talking about charsets. Somewhere there's a place where you can choose HOW to save the document. Find it and see how it was saving it (prolly as 1252 but who knows).
Third: decide which you want to use. To see how your server is serving the page, at least in Firefox (I dunno in other browsers) go try to view the page, then hit CTRL-i. Or right-click on it and choose "view page info". One of those should list how the server is sending your page. If you can't change server settings, you could make sure your document is being saved the same way the server is sending it. Or, you could try what's preferred: save as UTF-8 (not Unicode, do not add a BOM and uncheck any options than mention adding a BOM), and possibly your server will send the document out as UTF-8 too, which would make them match.
When the server and how the document was saved match, set your meta tag to list whichever charset you've chosen. So, all three should match. Browsers get happy.
Also, you'll probably want that meta tag to be one of the first meta tags in the <head>. Once a browser sees confirmation of the charset, it will go back to the beginning and re-read the code. So have it do that as soon as possible.
(I got the above advice from Joel on Software about half-way down)