Question

How can I modify regular expression so it can also accept + in my URL

see: http://awakeningwithin.simpletix.com/Search/Lorem+/
… error

if your remove the symbol:
http://awakeningwithin.simpletix.com/Search/Lorem/
… it works.

<rule name="RewriteSearch" stopProcessing="true"> 
    <match url="^Search/([_0-9a-z-]+)" /> 
    <action type="Rewrite" url="Search.aspx?term={R:1}" /> 
</rule>

Answer 1

The plus + character in URL means SPACE (the same as %20).

1. Based on the above try this one: ^search/([-_0-9a-z\+ ]+)

2. If you see 404 error like this:

HTTP Error 404.11 – Not Found

The request filtering module is configured to deny a request that
contains a double escape sequence.

• go to IIS Manager, open Request Filter module (global .. or the one for specific site)
• choose Edit Feature Settings on side column (or via context menu)
• tick Allow double escaping

or use this code (place somewhere in web.config in website root folder):

<system.webServer>
    <security>
        <requestFiltering allowDoubleEscaping="true" />
    </security>
</system.webServer>

If #1 does not work, then do #1 AND #2.

TESTED on IIS 7.5 — works fine.