Short answer: Take out the essential information from that HTML snippet and write it in your description in plain text. The same information is conveyed and there should be no problem. Like thus:
Music from "Reappear" by Chris Zabriskie (CC BY 3.0)
http://freemusicarchive.org/music/Chris_Zabriskie/Reappear
The whole point of the CC Attribution (CC BY) license is that you're free to use the work as long as you credit the original author in some way.
Long answer: To quote from the full legal code, what the Creative Commons Attribution license requires you to do is:
[Section 4(a)] You must ... keep intact all copyright notices for the Work and provide, reasonable to the medium or means You are utilizing: (i) the name of the Original Author (or pseudonym, if applicable) if supplied, ... (ii) the title of the Work if supplied; (iii) to the extent reasonably practicable, the URI, if any, that Licensor specifies to be associated with the Work, unless such URI does not refer to the copyright notice or licensing information for the Work; and (iv) , consistent with Section 3(b), in the case of an Adaptation, a credit identifying the use of the Work in the Adaptation (e.g., "French translation of the Work by Original Author," or "Screenplay based on original Work by Original Author")
(I skipped parts irrelevant to your case.)
Now, in your case, (i)="Chris Zabriskie", (ii)="Reappear", (iii)= "http://freemusicarchive.org/music/Chris_Zabriskie/Reappear" or "http://chriszabriskie.com/", and (iv) in your case is that you used the music in your video. These information are to be provided in the manner "reasonable to the medium or means You are utilizing". HTML is fine in places you can use it, but since you have to use plain text here, plain text would be the "reasonable" manner.
Most of the other parts in the HTML like rel="cc:attributionURL" property="cc:attributionName" is to make this license statement more easily readable by machines (so to say), and less for humans to read.
In addition, the author himself has clearly stated in his website that
The credit can be as simple as “Music by Chris Zabriskie” or “(insert song title) by Chris Zabriskie.” I prefer that the credit be included in the work itself (for example, on screen in a video rather than only in the description text). But as long as my name is associated with my work in the final version of the project, you’re welcome to use my songs free of charge.
(quoted from Licensing and Usage at chriszabriskie.com)
Best Answer
Make sure you are allowed to mark it as CC.
From here: http://www.youtube.com/t/creative_commons
Also,
From here: http://www.google.com/support/youtube/bin/answer.py?hl=en&answer=1284989