Conditional to compare segment_1 in the URL with the URI of a specified entry
In Twig you'll never, ever need to nest logic tags, within output tags or visa-versa.

The syntax you're looking for is:

{% set about_entry = craft.entries.id(17).first() %}

&lt;ul&gt;
    &lt;li {% if craft.request.getSegment(1) == about_entry.uri %}class="here"{% endif %}&gt;&lt;a href="{{ about_entry.url }}"&gt;{{ about_entry.title }}&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;