Selecting nodes by attribute value

For some reason I can't seem to select a specific node by the value of a
specified attribute, despite the fact that this is one of the basic things
described in any tutorial or reference on XSLT.  When I use the format:

...
<xsl:apply-templates select="element[@attributename=attributevalue]"/>
...

it just returns a blank page (or whatever might have been included up to
that point, such as formatting, like a background). It's as though its not
recognising that there's an attribute with the specified value (even though
there is, after double, triple, and quadruple checking to make sure I didn't
make a typo).  I've seen some examples with quotes around the attribute
value, but that just gives me an error messages in the browser: "required
whitespace missing".  It does work if I just use a number that would be the
equivalent node that I want, but I'd like to be able to specify by attribute
value.

I couldn't find an answer in the archives or elsewhere, so I'd really
appreciate it if anyone has any suggestions. I wouldn't be surprised if I'd
just missed out on something simple (that they don't tend to include in the
examples because they assume people know it already), since I've only just
started learning this.

Thanks,
-N



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