Mobile Redirect using htaccess

Tim Stone's solution is on the right track, but his initial rewriterule and and his cookie name in the final condition are different, and you can not write and read a cookie in the same request.

Here is the finalized working code:

RewriteEngine on
RewriteBase /
# Check if this is the noredirect query string
RewriteCond %{QUERY_STRING} (^|&)m=0(&|$)
# Set a cookie, and skip the next rule
RewriteRule ^ - [CO=mredir:0:www.website.com]

# Check if this looks like a mobile device
# (You could add another [OR] to the second one and add in what you
#  had to check, but I believe most mobile devices should send at
#  least one of these headers)
RewriteCond %{HTTP:x-wap-profile} !^$ [OR]
RewriteCond %{HTTP:Profile}       !^$ [OR]
RewriteCond %{HTTP_USER_AGENT} "acs|alav|alca|amoi|audi|aste|avan|benq|bird|blac|blaz|brew|cell|cldc|cmd-" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "dang|doco|eric|hipt|inno|ipaq|java|jigs|kddi|keji|leno|lg-c|lg-d|lg-g|lge-" [NC,OR]
RewriteCond %{HTTP_USER_AGENT}  "maui|maxo|midp|mits|mmef|mobi|mot-|moto|mwbp|nec-|newt|noki|opwv" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "palm|pana|pant|pdxg|phil|play|pluc|port|prox|qtek|qwap|sage|sams|sany" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "sch-|sec-|send|seri|sgh-|shar|sie-|siem|smal|smar|sony|sph-|symb|t-mo" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "teli|tim-|tosh|tsm-|upg1|upsi|vk-v|voda|w3cs|wap-|wapa|wapi" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "wapp|wapr|webc|winw|winw|xda|xda-" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "up.browser|up.link|windowssce|iemobile|mini|mmp" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "symbian|midp|wap|phone|pocket|mobile|pda|psp" [NC]
RewriteCond %{HTTP_USER_AGENT} !macintosh [NC]

# Check if we're not already on the mobile site
RewriteCond %{HTTP_HOST}          !^m\.
# Can not read and write cookie in same request, must duplicate condition
RewriteCond %{QUERY_STRING} !(^|&)m=0(&|$) 

# Check to make sure we haven't set the cookie before
RewriteCond %{HTTP_COOKIE}        !^.*mredir=0.*$ [NC]

# Now redirect to the mobile site
RewriteRule ^ http://m.website.com [R,L]

I tested bits and pieces of the following, but not the complete rule set in its entirety, so if you run into trouble with it let me know and I'll dig around a bit more. However, assuming I got everything correct, you could try something like the following:

RewriteEngine On

# Check if this is the noredirect query string
RewriteCond %{QUERY_STRING} (^|&)noredirect=true(&|$)
# Set a cookie, and skip the next rule
RewriteRule ^ - [CO=mredir:0:%{HTTP_HOST},S]

# Check if this looks like a mobile device
# (You could add another [OR] to the second one and add in what you
#  had to check, but I believe most mobile devices should send at
#  least one of these headers)
RewriteCond %{HTTP:x-wap-profile} !^$ [OR]
RewriteCond %{HTTP:Profile}       !^$
# Check if we're not already on the mobile site
RewriteCond %{HTTP_HOST}          !^m\.
# Check to make sure we haven't set the cookie before
RewriteCond %{HTTP:Cookie}        !\smredir=0(;|$)
# Now redirect to the mobile site
RewriteRule ^ http://m.example.org%{REQUEST_URI} [R,L]

I modified Tim Stone's solution even further. This allows the cookie to be in 2 states, 1 for mobile and 0 for full. When the mobile cookie is set to 0 even a mobile browser will go to the full site.

Here is the code:

<IfModule mod_rewrite.c>
    RewriteBase /
    RewriteEngine On

    # Check if mobile=1 is set and set cookie 'mobile' equal to 1
    RewriteCond %{QUERY_STRING} (^|&)mobile=1(&|$)
    RewriteRule ^ - [CO=mobile:1:%{HTTP_HOST}]

    # Check if mobile=0 is set and set cookie 'mobile' equal to 0
    RewriteCond %{QUERY_STRING} (^|&)mobile=0(&|$)
    RewriteRule ^ - [CO=mobile:0:%{HTTP_HOST}]

    # cookie can't be set and read in the same request so check
    RewriteCond %{QUERY_STRING} (^|&)mobile=0(&|$)
    RewriteRule ^ - [S=1]

    # Check if this looks like a mobile device
    RewriteCond %{HTTP:x-wap-profile} !^$ [OR]
    RewriteCond %{HTTP_USER_AGENT} "android|blackberry|ipad|iphone|ipod|iemobile|opera mobile|palmos|webos|googlebot-mobile" [NC,OR]
    RewriteCond %{HTTP:Profile}       !^$

    # Check if we're not already on the mobile site
    RewriteCond %{HTTP_HOST}          !^m\.
    # Check to make sure we haven't set the cookie before
    RewriteCond %{HTTP:Cookie}        !\mobile=0(;|$)
    # Now redirect to the mobile site
    RewriteRule ^ http://m.example.com%{REQUEST_URI} [R,L]
</IfModule>