linuxdoc validation improvement

using entities ] [ and & instead of the literals to improve
validation; replacing HTML <a href=""> with <url url="">

LDP/howto/linuxdoc/FBB.sgml

@@ -477,7 +477,7 @@ trying to translate original manuals
 from Spanish into English, but it is a hard work.
 Any good 'Spanish-to-English'
 translator is welcomed to contact me:
-skoric at eunet dot rs
+skoric at eunet dot rs</em>
 
 <p>
 Protus offers several interesting features:
@@ -579,7 +579,7 @@ radio BBS, using Protus type of, so called, <em>c_filter</em>:
       for Protus utility to be activated. In all
       connections to your BBS (including console),
       you should see a line like this: <bf>{PROTUS-4.0}</bf>
-      just after the well known line [[FBB-7.00-AB1FHMRX$]. It
+      just after the well known line &lsqb;&lsqb;FBB-7.00-AB1FHMRX$&rsqb;. It
       only gives an information that Protus is active on the
       system. Users of your BBS who don't have
       their passwords, connect just normally as before.
@@ -3326,7 +3326,7 @@ naredba VIEW
 
 naredbom VIEW moze se "pogledati" sta sadrzi neki arhivirani fajl.
 To su svi fajlovi sa: .ARJ .ZIP .LZH .ARC nastavcima.
-Primer: VIEW SP&YAPP.ARJ
+Primer: VIEW SP&amp;YAPP.ARJ
 
 @@ 9 XGET|XPUT|X1GET|ZGET
 
@@ -4805,7 +4805,7 @@ License, Version 1.1 or any later version published by the
 Free Software Foundation; with no Invariant Sections,
 with no Front-Cover Texts, and with no Back-Cover Texts.
 A copy of the license is available from
-<a href="http://www.fsf.org/licenses/fdl.html">http://www.fsf.org/licenses/fdl.html</a>.
+<url url="http://www.fsf.org/licenses/fdl.html">.
 
 <sect1>Disclaimer
 <p>