Canonical tags on filtered pages

Selected answers from the Dumb SEO Questions Facebook & G+ community.

• 
  Atit Dave: Hello All,
   ;
  We have one site named http://www.bargains-online.com.au/ & have some categories along with filter option on left side like filter by price & by brand, ect.
   ;
  We have already set rel canonical tags on all filtered pages, but still those all pages showing duplicate page titles and description warning in HTML Improvements section in Google Webmaster Tool.
   ;
  For Example:
  http://www.bargains-online.com.au/pressure-cleaners.html
   ;
  We've set rel canonical tag on below pages.
  http://www.bargains-online.com.au/pressure-cleaners/l/manufacturer:black-eagle.html
  http://www.bargains-online.com.au/pressure-cleaners/l/price:2,100.html
  http://www.bargains-online.com.au/pressure-cleaners/l/price:3,100.html
   ;
  Kindly request if anybody has any solutions for the same, please share with us.
   ;
  Thanks,
  Dave
• 
  Jon Tromans: How long ago did you make the canonical changes? ;
• 
  Atit Dave: +Jon Tromans ; the canonical changes was done before 4-5 months ago.
• 
  Tony “Tiggerito” McCreath: On your second example I checked the cache and it contained a self referencing canonical:
  
  <link rel="canonical" href="http://www.bargains-online.com.au/pressure-cleaners/l/price:2,100.html" />
  
  So it seems Google has not recrawled those pages since you changed how you do those canonicals.
• 
  Tim Capper: Canonical's  ;were not properly implemented and need to be recrawled
  
  Looking at ;/l/price:3,100.html.  ; it was last cached 12 May, with an incorrect Canonical ;
  
  Patience : )