different first element in a list

I have an Xml list, for esample this list of skills:

<skills>
    <skill mark="excellent" name="excellentskill">
    <skill mark="excellent" name="excellent skill">
    <skill mark="good" name="goodskill">
    <skill mark="good" name="goodskill">
    <skill mark="basic" name="basicskill">
    <skill mark="basic" name="basicskill">
    <skill mark="excellent" name="excellentskill">
    <skill mark="good" name="goodskill">
    <skill mark="basic" name="basicskill">
</skills>

and I want to list in groups based on 'mark' attribute:

excellentskill
excellentskill
excellentskill
goodskill
goodskill
goodskill
basicskill
basicskill
basicskill

rendering only the first element of each group in a different way:

<b>excellentskill</b>
excellentskill
excellentskill
<b>goodskill</b>
goodskill
goodskill
<b>basicskill</b>
basicskill
basicskill

How can I?

What I want to obtain is an xhtml list like this

excellent skills:   excellentskill
                    excellentskill
                    excellentskill
good skills:        goodskill
                    goodskill
                    goodskill
basic skills:       basicskill
                    basicskill
                    basicskill

using <div>s or <table>s

Thank you very much for your help :)
____________________________________________________________________________
Lorenzo De Tomasi, student of Information Architecture, Interface Design and
Visual Design
via Bellaria 6, 21018 Sesto Calende (Varese), Italia
phone: +39 (0)331 924649
mobile: +39 329 3941065; +39 333 8979304
e-mail: lorenzo.detomasi@xxxxxxxxx; lorenzo.detomasi@xxxxxxxx
website: http://biografica.tzone.it
ICQ uin: 11313132
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