title: identify the correct CSS selector of a url for an R script
body: <p>I am trying to obtain data from a website and thanks to a helper i could get to the following script:</p>
  
  <pre><code>require(httr)
  require(rvest)
        res &lt;- httr::POST(url = "http://apps.kew.org/wcsp/advsearch.do", 
                      body = list(page = "advancedSearch", 
                                  AttachmentExist = "", 
                                  family = "", 
                                  placeOfPub = "", 
                                  genus =      "Arctodupontia", 
                                  yearPublished = "", 
                                  species ="scleroclada", 
                                  author = "", 
                                  infraRank = "", 
                                  infraEpithet = "", 
                                  selectedLevel = "cont"), 
                      encode = "form") 
    pg &lt;- content(res, as="parsed")
    lnks &lt;- html_attr(html_node(pg,"td"), "href")
  </code></pre>
  
  <p>However, in some cases, like the example above, it does not retrieve the right link because, for some reason, html_attr does not find urls ("href") within the node detected by html_node. So far, i have tried different CSS selector, like "td", "a.onwardnav" and ".plantname" but none of them generate an object that html_attr can handle correctly. 
  Any hint?</p>