Gujarati is popular enough to be supported by most modern systems by default. I never installed anything special, but I just checked up: I have it on my Windows XP and Windows 7 systems.
So, all you need it to write the text and save it in UTF-8. You should always prescribe this Unicode UTF in HTTP-EQUIV:
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
This is very important: even if your HTTP server supports UTF-8 by its default settings, HTTP-EQUIV is still critical: if someone saves the HTML file locally, the charset information would be lost without it.
That's it. You page will support combination of wide set of different languages at the same time.
Also, just in case you use ASP.NET and want to go in for globalization and then localization: http://msdn.microsoft.com/en-us/library/c6zyy3s9.aspx