Is it worth a back-end developer's time to get into web-design and HTML/CSS
raffi: I'll avoid me too and agree you should learn these front end technologies.  That said, there seems to be a question of how and what underlying your post.  I'm not a designer by any stretch of the imagination, still I hope this helps:== XHTML/CSS ==1. Learn basic HTML, understand what "semantic markup" means.  I assume you know some HTML already.2. To understand CSS, understand the box model.  Understand inline and block elements.  Understand selectors.  Understand positioning.  The rest of it falls in place from there.Hopefully you'll have an appreciation for markup and meaning versus presentation at this point.== JavaScript ==3. Learn Javascript.  Understand that everything is a hashtable.  Understand how it handles scoping and understand classless objects.  Once you're comfortable with this you're ready to move on.4. Understand the DOM and how to manipulate it.5. Read a little on AJAX, I found the DHTML utopia book on Sitepoint.com?myaffiliateid=me was good.6. After you understand AJAX and DOM, go learn a library like JQuery or whatever else people advocate these days.  These libraries are like mana from heaven.  They will save you time!  Oh, if you did steps 3-5 you'll be productive with a JS library in about 2 minutes.  The learning curve is small at this point.  Great stuff!7. Install Firebug and spend an hour or two learning how to use it.  Firebug will save you time and console.log is so much better than alert().  Firebug has made me happy.Now you know how to manipulate sites on the client side.  Great!  Last step:== Graphics ==8. Learn a tool like Photoshop or the GIMP.  Understand how to select stuff, copy and paste.  Then become familiar with layers and masking.  I am not a graphics guy but I've only recently become turned on to the power of masking.  Wow.  People like you and I can do neat things.I don't have resources for everything because I scrimped and learned as I went.  However this should represent a good order (and some pointers on what to look at) as you pursue this.  Good luck!