Firefox 3 for developers

The Firefox 3 seems to be officially release. This is very exciting thing, but not for all of developers who needs to support a new version of the browser.

So I just want to have a quick overview what should be done to prepare web sites for new version of Firefox 3 base on the article: Firefox 3 for developers.

The most valuable part for me is Updating web applications for Firefox 3.


I cannot see a lot of changes in the DOM (which is a good thing from the point of support). The one is using importNode to copy a node from an external document.



Character set inheritance

Now, frames are only allowed to inherit the parent's character set if both frame and parent were loaded from the same server. So, make sure If you have pages that assume that frames loaded from other servers will inherit the same character set, you should update the frames' HTML to indicate their character set specifically.

Change to the script element

The <script> element in text/html documents now requires a closing </script> in HTML 4 documents. So, you should replace:

<script ... />


<script ...></script>



Change to font-size based on em, ex units

font-size values in em and ex units used to be affected by the user's minimum font size setting... font-size values in em and ex units are now based on an "intended font size" that is not affected by the user's minimum font size. In other words, font sizes are always calculated according to the designer's intention and are adjusted for minimum font size afterwards.

So check your font sizes with em an ex units.


Security Changes

Chrome Access

Firefox 3 only allows web content to access items in the chrome://browser/ and chrome://toolkit/ spaces. These files are intended to be accessible by web content. All other chrome content is now blocked from access by the web.

So check your Chrome applications.


File Uploads

Now only the filename itself is available to the web application. Previously full path to the file was available (sometimes) at the server.

Make sure you don't rely on the full file path on the client.


Firefox 3 supports JavaScript 1.8.

Script object is no longer supported. It should not affect usual web site anyway.


So it looks like there's not much to update your web site for Firefox 3. I hope it will not be a big deal. I'll try to have a look at the new stuff in the JavaScrip 1.8 later.

Very exciting thing in that FF 3 has Microformats support. So Semantic Web will move on faster (hopefully) after it.