Or maybe you call it "sharp" - the # symbol.
I've came across one instance, where #! and # used simultaneously in a single URL. From reading other articles, including RFC, I can't understand whether that is a legal combination or not. When encountering such page Mozilla browser (Iceweasel in this case) displays the URL as having 2 #'s, while Chrome displays only one, but dies shortly afterwards (the tab containing the page becomes unresponsive and crashes - but it may not be connected).
Now, my question is, is it legal to have both in one URL, is it maybe legal and redundant (should be normalized), or is it just a bug in Mozilla browser? So, suppose I'm making an AJAX request, or trying to navigate the browser history - what should I do, if I encounter this situation?
RFC-3986: http://tools.ietf.org/html/rfc3986#section-3.4 , which should be clarifying it... just in case.
Also: https://developers.google.com/webmasters/ajax-crawling/docs/specification how Google crawlers see things.
The format for a fragment only allows slashes, question marks, and
pchars. If you look up the RFC, you'll see that the hash mark is not a valid
However, browsers will try their best to read non-valid URLs by treating repeat hashes as though they are escaped, as you can see by checking the value of
window.location.hash (in IE, Firefox, and Chrome) for
which is the same
It may be legal as @apsillers mentioned. But I would avoid it unless necessary as it can cause a certain confusion concerning the url.
That kind of url:
Seems really confusing to me and will be even more confusing to regular users and maybe search engines.
My answer is a clear no, at least when referring to RFC 3986. But you have to look at more than just 3.4
Section 3 defines the structure of an URI as follows:
foo://example.com:8042/over/there?name=ferret#nose \_/ \______________/\_________/ \_________/ \__/ | | | | | scheme authority path query fragment
(I just took the upper part, relevant for URLs)
So, to answer your question, you have to look at all the parts:
ALPHA *( ALPHA / DIGIT / "+" / "-" / ".")
So, no hashes allowed so far except for terminating the URI, which is not what we want, if would like to use at least one hash ;-)
To sum up: Only one "#" is allowed in a compliant URL (or URI) as the marker for the URL-fragment. Especially hash signes that are supposed to be in the path (at least from the looks, as there are slashes afterwards) are problematic as they officially terminate the path part.
This can cause problems e.g. in single page applications where this is used because the navigation after the hash is done on client side not on the server. In this case, the SPA should make sure, it correctly handles the rest of the URL on reception which can include the possibly (browser specific) URL-encoded query and fragment .
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