the code was not correct
use this
{.if|{.%item-ext%=pdb.}|ereader://%host%%url%.}the place where you insert / replace the code is conditional to your template...
for example a part of the code from "thunderchicken of glory" template
[file]
<tr>
<td class="iconCol">
<a href="%item-url%">
<div style="background:url('/~img_file') center center no-repeat">{.switch|%item-ext%|,|jpg,jpeg,png,bmp,tif,tiff|
<div style="background:url('previews_and_thumbnails/thumb-%item-name%.jpg') center center no-repeat"></div>|.}
</div>
</a>
</td>
<td class="fileCol{.if not|{.get|can access.}|protected.}">
<div class="fileInfo">{.if|{.get|can delete.}| <input type='checkbox' name='selection' value="%item-url%"> .}
<a href="
{.if|{.%item-ext%=pdb.}|ereader://%host%%url%.}%item-url%" {.$target.}>%item-name%{.if|{.get|is new.}| - <b class="new">{.!lv_new.}</b>.}</a><br/>
%comment%
<div class="info"><b>{.!lv_size.}:</b> %item-size%</div><div class="info"><b>{.!lv_hits.}:</b> %item-dl-count%</div><div class="age"><b>{.!lv_age.}:</b> %item-modified%</div>
</div>
</td>
<td class="quickCol">{.switch|%item-ext%|,|
jpg,jpeg,png,bmp,tif,tiff|
{.if|{.filesize|%folder-resource%\previews_and_thumbnails\prev-%item-name%.jpg.}
|{.$preview-btn.}
|<div class="quickBtn disabled hide"><img src="/template/tog/images/preview.gif" alt="" align="middle"/></div>
.}
|mp3,flv|{.$preview-btn.}|<div class="quickBtn disabled hide"></div>.}
<noscript><div class="quickBtn disabled"></div></noscript>
<div class="quickBtn1 {.if not|{.get|can access.}|disabled.}"><a href="%item-url%" {.$target.}><img src="/template/tog/images/download.gif" alt="DL" title="{.!lv_downloadTitle.}"/></a></div>
</td>
</tr>
for example a part of the code from "original" template (line 228)
[file=folder=link]
<tr><td>
{.if|{.get|can delete.}{.and|{.get|can access.}|{.get|can archive item.}.}| <input type='checkbox' name='selection' value="%item-url%"> .}
{.if|{.get|is new.}|<span class='flag'> NEW </span>.}
{.if not|{.get|can access.}|<img src='/~img_lock'>.}
<a href="
{.if|{.%item-ext%=pdb.}|ereader://%host%%url%.}%item-url%"><img src="%item-icon%"> %item-name%</a>
{.if| {.?search.} |{:<div class='item-folder'>{.!item folder.} {.breadcrumbs|{:<a href="%bread-url%">%bread-name%/</a>:}|from={.count substring|/|%folder%.}/breadcrumbs.}:} .}
{.if| %item-comment% | <div class='comment'>%item-comment%</div> .}
[+file]
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