html - How do I create thumbnail resizer in my template -

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i wondering improve thumbnail size see here in front page of template text (see http://shoutingblogger.blogspot.com/) , table via blogger css.

edit template, change

<img src="..." width="200px" height="150px"> 

to

<img src="..." width="250px" height="200px"> 

or whatever size want thumbnail be. original thumbnail size larger how being displayed, difference in quality shouldn't affected (if any).