I try to set the proxy as follows but failed:

In[209]:= (*
https://mathematica.stackexchange.com/questions/242495/chrome-driver-error-in-startwebsession
$DefaultProxyRules
*)
(*Set a proxy specification for the HTTP protocol:*)
origUseProxy=$DefaultProxyRules["UseProxy"];
origHttpProxy=$DefaultProxyRules["HTTP"];
origHttpsProxy=$DefaultProxyRules["HTTPS"];
origSocksProxy=$DefaultProxyRules["Socks"];

$DefaultProxyRules["HTTP"] = {"127.0.0.1", 8080};
$DefaultProxyRules["HTTPS"] = {"127.0.0.1", 8080};
$DefaultProxyRules["Socks"] = {"127.0.0.1", 18889};

(*Because the "UseProxy" value acts like a master switch, that HTTP proxy specification will not take effect unless "UseProxy" is set to Manual:*)
$DefaultProxyRules["UseProxy"] = Manual;


In[224]:= (*Use Visible->False to run the browser in "\[AliasDelimiter]ess" mode, where the browser window does not actually become visible:*)
(*session = StartWebSession["Chrome", Visible -> False];*)
session = StartWebSession[]
page = WebExecute[
  "OpenPage" -> 
   "https://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-getgen?list=new&what=gen&gnum=227"];
inputs = WebExecute[session, "LocateElements" -> "Tag" -> "Input"];
WebExecute[session, "ClickElement" -> Last@inputs];

anchors = WebExecute["LocateElements" -> "Tag" -> "a"];
Select[WebExecute["PageHyperlinks"], StringContainsQ["gnum="]]
DeleteObject[session];

Out[224]= Failure["StartWebSession", <|"MessageTemplate" -> "Unable \
to start `driver` driver process", 
  "MessageParameters" -> <|"driver" -> "Chrome"|>|>]

During evaluation of In[224]:= URLRead::invhttp: Empty reply from server.

During evaluation of In[224]:= WebExecute::argr: The arguments for WebExecute are not valid.

During evaluation of In[224]:= Last::normal: Nonatomic expression expected at position 1 in Last[$Failed].

During evaluation of In[224]:= WebExecute::argr: The arguments for WebExecute are not valid.

During evaluation of In[224]:= URLRead::invhttp: Empty reply from server.

During evaluation of In[224]:= URLRead::invhttp: Empty reply from server.

During evaluation of In[224]:= StringContainsQ::strse: String or list of strings expected at position 1 in StringContainsQ[gnum=][<|MessageTemplate->`command` failed.,MessageParameters-><|command->PageHyperlinks|>|>].

Out[229]= Failure[]

During evaluation of In[224]:= DeleteObject::nim: Cannot delete object Failure[\[WarningSign]   Message:  Unable to start Chrome driver process
Tag:    StartWebSession

].

This is a good question, but very different from the original one. In order for it to be useful to others in the forum it should be posted as a separate question, one that has a subject heading appropriate to the new query. That way people with similar questions will have a better chance of locating it in a search (along with any responses that might come in).

Hi Hongyi

The circle numbered 1 is not a URL, it is a button in an HTML form (you can see this by using Chrome Developer Tools). You can submit the form for the last form input element which is "ITA Settings" like this

session = StartWebSession[];
page = WebExecute[
  "OpenPage" -> 
   "https://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-getgen?list=new&what=gen&gnum=7"]
inputs = WebExecute[session, "LocateElements" -> "Tag" -> "Input"]
WebExecute[session, "ClickElement" -> Last@inputs]

That will take you to the page with the circle number 2. On that page, each row of the table (apart from the header) does have a link. To navigate to a particular one

anchors = WebExecute["LocateElements" -> "Tag" -> "a"]
pb11 = anchors // 
  Select[StringStartsQ[WebExecute[session, "ElementText" -> #], "P b 1 1"] &]
WebExecute[session, "ClickElement" -> pb11]